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Terms in this set (51)

One of the world's best known and most widely read and studied philosophers.

He was the student of Socrates and the teacher of Aristotle.

Though influenced primarily by Socrates, to the extent that Socrates is usually the main character in many of Plato's writings, he was also influenced by Heraclitus, Parmenides, and the Pythagoreans.

Nonetheless, his earliest works are generally regarded as the most reliable of the ancient sources on Socrates, and the character Socrates that we know through these writings is considered to be one of the greatest of the ancient philosophers.

His "The Republic" speaks for itself by having the main character speak Plato's philosophy. These works blend ethics, political philosophy, moral psychology, epistemology, and metaphysics into an interconnected and systematic philosophy.

Provided the theory of Forms, according to which the world we know through the senses is only an imitation of the pure, eternal, and unchanging world of the Forms. Plato's works also contain the origins of the familiar complaint that the arts work by inflaming the passions, and are mere illusions. We also are introduced to the ideal of "Platonic love:" Plato saw love as motivated by a longing for the highest Form of beauty—The Beautiful Itself, and love as the motivational power through which the highest of achievements are possible. Because they tended to distract us into accepting less than our highest potentials, however, Plato mistrusted and generally advised against physical expressions of love.
A towering figure in ancient Greek philosophy, contributing to logic, metaphysics, mathematics, physics, biology, botany, ethics, politics, agriculture, medicine, dance and theatre.

A student of Plato who in turn studied under Socrates. He was more empirically-minded than Plato or Socrates and is famous for rejecting Plato's theory of forms.

Aristotle radically transformed most, if not all, areas of knowledge he touched. It is no wonder that Aquinas referred to him simply as "The Philosopher."

In his lifetime, Aristotle wrote as many as 200 treatises, of which only 31 survive. Unfortunately for us, these works are in the form of lecture notes and draft manuscripts never intended for general readership, so they do not demonstrate his reputed polished prose style which attracted many great followers, including the Roman Cicero. Aristotle was the first to classify areas of human knowledge into distinct disciplines such as mathematics, biology, and ethics. Some of these classifications are still used today.

As the father of the field of logic, he was the first to develop a formalized system for reasoning. Aristotle observed that the validity of any argument can be determined by its structure rather than its content. A classic example of a valid argument is his syllogism: All men are mortal; Socrates is a man; therefore, Socrates is mortal. Given the structure of this argument, as long as the premises are true, then the conclusion is also guaranteed to be true. Aristotle's brand of logic dominated this area of thought until the rise of modern propositional logic and predicate logic 2000 years later.

Aristotle's emphasis on good reasoning combined with his belief in the scientific method forms the backdrop for most of his work. For example, in his work in ethics and politics, Aristotle identifies the highest good with intellectual virtue; that is, a moral person is one who cultivates certain virtues based on reasoning. And in his work on psychology and the soul, Aristotle distinguishes sense perception from reason, which unifies and interprets the sense perceptions and is the source of all knowledge.

Aristotle famously rejected Plato's theory of forms, which states that properties such as beauty are abstract universal entities that exist independent of the objects themselves. Instead, he argued that forms are intrinsic to the objects and cannot exist apart from them, and so must be studied in relation to them. However, in discussing art, Aristotle seems to reject this, and instead argues for idealized universal form which artists attempt to capture in their work.

Aristotle was the founder of the Lyceum, a school of learning based in Athens, Greece; and he was an inspiration for the Peripatetics, his followers from the Lyceum.
René Descartes is often credited with being the "Father of Modern Philosophy." This title is justified due both to his break with the traditional Scholastic-Aristotelian philosophy prevalent at his time and to his development and promotion of the new, mechanistic sciences. His fundamental break with Scholastic philosophy was twofold. First, Descartes thought that the Scholastics' method was prone to doubt given their reliance on sensation as the source for all knowledge. Second, he wanted to replace their final causal model of scientific explanation with the more modern, mechanistic model.

Descartes attempted to address the former issue via his method of doubt. His basic strategy was to consider false any belief that falls prey to even the slightest doubt. This "hyperbolic doubt" then serves to clear the way for what Descartes considers to be an unprejudiced search for the truth. This clearing of his previously held beliefs then puts him at an epistemological ground-zero. From here Descartes sets out to find something that lies beyond all doubt. He eventually discovers that "I exist" is impossible to doubt and is, therefore, absolutely certain. It is from this point that Descartes proceeds to demonstrate God's existence and that God cannot be a deceiver. This, in turn, serves to fix the certainty of everything that is clearly and distinctly understood and provides the epistemological foundation Descartes set out to find.

Once this conclusion is reached, Descartes can proceed to rebuild his system of previously dubious beliefs on this absolutely certain foundation. These beliefs, which are re-established with absolute certainty, include the existence of a world of bodies external to the mind, the dualistic distinction of the immaterial mind from the body, and his mechanistic model of physics based on the clear and distinct ideas of geometry. This points toward his second, major break with the Scholastic Aristotelian tradition in that Descartes intended to replace their system based on final causal explanations with his system based on mechanistic principles. Descartes also applied this mechanistic framework to the operation of plant, animal and human bodies, sensation and the passions. All of this eventually culminating in a moral system based on the notion of "generosity."

The presentation below provides an overview of Descartes' philosophical thought as it relates to these various metaphysical, epistemological, religious, moral and scientific issues, covering the wide range of his published works and correspondence.
John Locke (1632-1704) presents an intriguing figure in the history of political philosophy whose brilliance of exposition and breadth of scholarly activity remains profoundly influential.

Locke proposed a radical conception of political philosophy deduced from the principle of self-ownership and the corollary right to own property, which in turn is based on his famous claim that a man earns ownership over a resource when he mixes his labour with it. Government, he argued, should be limited to securing the life and property of its citizens, and is only necessary because in an ideal, anarchic state of nature, various problems arise that would make life more insecure than under the protection of a minimal state. Locke is also renown for his writings on toleration in which he espoused the right to freedom of conscience and religion (except when religion was deemed intolerant!), and for his cogent criticism of hereditary monarchy and patriarchalism. After his death, his mature political philosophy leant support to the British Whig party and its principles, to the Age of Enlightenment, and to the development of the separation of the State and Church in the American Constitution as well as to the rise of human rights theories in the Twentieth Century.

However, a closer study of any philosopher reveals aspects and depths that introductory caricatures (including this one) cannot portray, and while such articles seemingly present a completed sketch of all that can ever be known of a great thinker, it must always be remembered that a great thinker is rarely captured in a few pages or paragraphs by a lesser one, or one that approaches him with particular philosophical interest or bias: the reader, once contented with the glosses provided here, should always return to and scrutinise Locke in the original - just as an academic exposition of Beethoven's Eroica symphony will always be a sallow reflection of the actual music.

This article summarises the general drift of Locke's political thinking, leaving the other IEP article on Locke to examine his general philosophy and his theory of knowledge. The article touches on his biography as it relates to the development of his political thought, and it also provides an analysis of some of the issues that his philosophy raises - especially with regards to the Two Treatises of Government. Locke is rightly famous for his Treatises, yet during his life he repudiated his authorship, although he subtly recommended them as essential reading in letters and thoughts on reading for gentlemen. The Treatises swiftly became a classic in political philosophy, and its popularity has remained undiminished since his time: the 'John Locke academic industry' is vibrant and broad with an academic journal (John Locke Studies) and books regularly coming out dealing with his philosophy.
Socrates is one of the few individuals whom one could say has so-shaped the cultural and intellectual development of the world that, without him, history would be profoundly different. He is best known for his association with the Socratic method of question and answer, his claim that he was ignorant (or aware of his own absence of knowledge), and his claim that the unexamined life is not worth living, for human beings. He was the inspiration for Plato, the thinker widely held to be the founder of the Western philosophical tradition. Plato in turn served as the teacher of Aristotle, thus establishing the famous triad of ancient philosophers: Socrates, Plato, and Aristotle. Unlike other philosophers of his time and ours, Socrates never wrote anything down but was committed to living simply and to interrogating the everyday views and popular opinions of those in his home city of Athens. At the age of 70, he was put to death at the hands of his fellow citizens on charges of impiety and corruption of the youth. His trial, along with the social and political context in which occurred, has warranted as much treatment from historians and classicists as his arguments and methods have from philosophers.

This article gives an overview of Socrates: who he was, what he thought, and his purported method. It is both historical and philosophical. At the same time, it contains reflections on the difficult nature of knowing anything about a person who never committed any of his ideas to the written word. Much of what is known about Socrates comes to us from Plato, although Socrates appears in the works of other ancient writers as well as those who follow Plato in the history of philosophy. This article recognizes that finding the original Socrates may be impossible, but it attempts to achieve a close approximation.
Nietzsche was a German philosopher, essayist, and cultural critic. His writings on truth, morality, language, aesthetics, cultural theory, history, nihilism, power, consciousness, and the meaning of existence have exerted an enormous influence on Western philosophy and intellectual history.

Nietzsche spoke of "the death of God," and foresaw the dissolution of traditional religion and metaphysics. Some interpreters of Nietzsche believe he embraced nihilism, rejected philosophical reasoning, and promoted a literary exploration of the human condition, while not being concerned with gaining truth and knowledge in the traditional sense of those terms. However, other interpreters of Nietzsche say that in attempting to counteract the predicted rise of nihilism, he was engaged in a positive program to reaffirm life, and so he called for a radical, naturalistic rethinking of the nature of human existence, knowledge, and morality. On either interpretation, it is agreed that he suggested a plan for "becoming what one is" through the cultivation of instincts and various cognitive faculties, a plan that requires constant struggle with one's psychological and intellectual inheritances.

Nietzsche claimed the exemplary human being must craft his/her own identity through self-realization and do so without relying on anything transcending that life—such as God or a soul. This way of living should be affirmed even were one to adopt, most problematically, a radical vision of eternity, one suggesting the "eternal recurrence" of all events. According to some commentators, Nietzsche advanced a cosmological theory of "will to power." But others interpret him as not being overly concerned with working out a general cosmology. Questions regarding the coherence of Nietzsche's views--questions such as whether these views could all be taken together without contradiction, whether readers should discredit any particular view if proven incoherent or incompatible with others, and the like--continue to draw the attention of contemporary intellectual historians and philosophers.
Better known in China as "Master Kong" (Chinese: Kongzi), Confucius was a fifth-century BCE Chinese thinker whose influence upon East Asian intellectual and social history is immeasurable. As a culturally symbolic figure, he has been alternately idealized, deified, dismissed, vilified, and rehabilitated over the millennia by both Asian and non-Asian thinkers and regimes. Given his extraordinary impact on Chinese, Korean, Japanese, and Vietnamese thought, it is ironic that so little can be known about Confucius. The tradition that bears his name - "Confucianism" (Chinese: Rujia) - ultimately traces itself to the sayings and biographical fragments recorded in the text known as the Analects (Chinese: Lunyu). As with the person of Confucius himself, scholars disagree about the origins and character of the Analects, but it remains the traditional source for information about Confucius' life and teaching. Most scholars remain confident that it is possible to extract from the Analects several philosophical themes and views that may be safely attributed to this ancient Chinese sage. These are primarily ethical, rather than analytical-logical or metaphysical in nature, and include Confucius' claim that Tian ("Heaven") is aligned with moral order but dependent upon human agents to actualize its will; his concern for li (ritual propriety) as the instrument through which the family, the state, and the world may be aligned with Tian's moral order; and his belief in the "contagious" nature of moral force (de), by which moral rulers diffuse morality to their subjects, moral parents raise moral children, and so forth.
Immanuel Kant (1724-1804) is one of the most influential philosophers in the history of Western philosophy. His contributions to metaphysics, epistemology, ethics, and aesthetics have had a profound impact on almost every philosophical movement that followed him. This article focuses on his metaphysics and epistemology in one of his most important works, The Critique of Pure Reason. A large part of Kant's work addresses the question "What can we know?" The answer, if it can be stated simply, is that our knowledge is constrained to mathematics and the science of the natural, empirical world. It is impossible, Kant argues, to extend knowledge to the supersensible realm of speculative metaphysics. The reason that knowledge has these constraints, Kant argues, is that the mind plays an active role in constituting the features of experience and limiting the mind's access only to the empirical realm of space and time.

Kant responded to his predecessors by arguing against the Empiricists that the mind is not a blank slate that is written upon by the empirical world, and by rejecting the Rationalists' notion that pure, a priori knowledge of a mind-independent world was possible. Reason itself is structured with forms of experience and categories that give a phenomenal and logical structure to any possible object of empirical experience. These categories cannot be circumvented to get at a mind-independent world, but they are necessary for experience of spatio-temporal objects with their causal behavior and logical properties. These two theses constitute Kant's famous transcendental idealism and empirical realism.

Kant's contributions to ethics have been just as substantial, if not more so, than his work in metaphysics and epistemology. He is the most important proponent in philosophical history of deontological, or duty based, ethics. In Kant's view, the sole feature that gives an action moral worth is not the outcome that is achieved by the action, but the motive that is behind the action. And the only motive that can endow an act with moral value, he argues, is one that arises from universal principles discovered by reason. The categorical imperative is Kant's famous statement of this duty: "Act only according to that maxim by which you can at the same time will that it should become a universal law."
Jean-Jacques Rousseau was one of the most influential thinkers during the Enlightenment in eighteenth century Europe. His first major philosophical work, A Discourse on the Sciences and Arts, was the winning response to an essay contest conducted by the Academy of Dijon in 1750. In this work, Rousseau argues that the progression of the sciences and arts has caused the corruption of virtue and morality. This discourse won Rousseau fame and recognition, and it laid much of the philosophical groundwork for a second, longer work, The Discourse on the Origin of Inequality. The second discourse did not win the Academy's prize, but like the first, it was widely read and further solidified Rousseau's place as a significant intellectual figure. The central claim of the work is that human beings are basically good by nature, but were corrupted by the complex historical events that resulted in present day civil society.Rousseau's praise of nature is a theme that continues throughout his later works as well, the most significant of which include his comprehensive work on the philosophy of education, the Emile, and his major work on political philosophy, The Social Contract: both published in 1762. These works caused great controversy in France and were immediately banned by Paris authorities. Rousseau fled France and settled in Switzerland, but he continued to find difficulties with authorities and quarrel with friends. The end of Rousseau's life was marked in large part by his growing paranoia and his continued attempts to justify his life and his work. This is especially evident in his later books, The Confessions, The Reveries of the Solitary Walker, and Rousseau: Judge of Jean-Jacques.

Rousseau greatly influenced Immanuel Kant's work on ethics. His novel Julie or the New Heloise impacted the late eighteenth century's Romantic Naturalism movement, and his political ideals were championed by leaders of the French Revolution.
The philosophical career of Jean Paul Sartre (1905-1980) focuses, in its first phase, upon the construction of a philosophy of existence known as existentialism. Sartre's early works are characterized by a development of classic phenomenology, but his reflection diverges from Husserl's on methodology, the conception of the self, and an interest in ethics. These points of divergence are the cornerstones of Sartre's existential phenomenology, whose purpose is to understand human existence rather than the world as such. Adopting and adapting the methods of phenomenology, Sartre sets out to develop an ontological account of what it is to be human. The main features of this ontology are the groundlessness and radical freedom which characterize the human condition. These are contrasted with the unproblematic being of the world of things. Sartre's substantial literary output adds dramatic expression to the always unstable co-existence of facts and freedom in an indifferent world.

Sartre's ontology is explained in his philosophical masterpiece, Being and Nothingness, where he defines two types of reality which lie beyond our conscious experience: the being of the object of consciousness and that of consciousness itself. The object of consciousness exists as "in-itself," that is, in an independent and non-relational way. However, consciousness is always consciousness "of something," so it is defined in relation to something else, and it is not possible to grasp it within a conscious experience: it exists as "for-itself." An essential feature of consciousness is its negative power, by which we can experience "nothingness." This power is also at work within the self, where it creates an intrinsic lack of self-identity. So the unity of the self is understood as a task for the for-itself rather than as a given.

In order to ground itself, the self needs projects, which can be viewed as aspects of an individual's fundamental project and motivated by a desire for "being" lying within the individual's consciousness. The source of this project is a spontaneous original choice that depends on the individual's freedom. However, self's choice may lead to a project of self-deception such as bad faith, where one's own real nature as for-itself is discarded to adopt that of the in-itself. Our only way to escape self-deception is authenticity, that is, choosing in a way which reveals the existence of the for-itself as both factual and transcendent. For Sartre, my proper exercise of freedom creates values that any other human being placed in my situation could experience, therefore each authentic project expresses a universal dimension in the singularity of a human life.

After a brief summary of Sartre's life, this article looks at the main themes characterizing Sartre's early philosophical works. The ontology developed in Sartre's main existential work, Being and Nothingness, will then be analysed. Finally, an overview is provided of the further development of existentialist themes in his later works.
"Hume is our Politics, Hume is our Trade, Hume is our Philosophy, Hume is our Religion." This statement by nineteenth century philosopher James Hutchison Stirling reflects the unique position in intellectual thought held by Scottish philosopher David Hume. Part of Hume's fame and importance owes to his boldly skeptical approach to a range of philosophical subjects. In epistemology, he questioned common notions of personal identity, and argued that there is no permanent "self" that continues over time. He dismissed standard accounts of causality and argued that our conceptions of cause-effect relations are grounded in habits of thinking, rather than in the perception of causal forces in the external world itself. He defended the skeptical position that human reason is inherently contradictory, and it is only through naturally-instilled beliefs that we can navigate our way through common life. In the philosophy of religion, he argued that it is unreasonable to believe testimonies of alleged miraculous events, and he hints, accordingly, that we should reject religions that are founded on miracle testimonies. Against the common belief of the time that God's existence could be proven through a design or causal argument, Hume offered compelling criticisms of standard theistic proofs. He also advanced theories on the origin of popular religious beliefs, grounding such notions in human psychology rather than in rational argument or divine revelation. The larger aim of his critique was to disentangle philosophy from religion and thus allow philosophy to pursue its own ends without rational over-extension or psychological corruption. In moral theory, against the common view that God plays an important role in the creation and reinforcement of moral values, he offered one of the first purely secular moral theories, which grounded morality in the pleasing and useful consequences that result from our actions. He introduced the term "utility" into our moral vocabulary, and his theory is the immediate forerunner to the classic utilitarian views of Jeremy Bentham and John Stuart Mill. He is famous for the position that we cannot derive ought from is, the view that statements of moral obligation cannot simply be deduced from statements of fact. Some see Hume as an early proponent of the emotivist metaethical view that moral judgments principally express our feelings. He also made important contributions to aesthetic theory with his view that there is a uniform standard of taste within human nature, in political theory with his critique of social contractarianism, and economic theory with his anti-mercantilist views. As a philosophical historian, he defended the conservative view that British governments are best run through a strong monarchy.
Abu 'Ali al-Husayn ibn Sina is better known in Europe by the Latinized name "Avicenna." He is probably the most significant philosopher in the Islamic tradition and arguably the most influential philosopher of the pre-modern era. Born in Afshana near Bukhara in Central Asia in about 980, he is best known as a polymath, as a physician whose major work the Canon (al-Qanun fi'l-Tibb) continued to be taught as a medical textbook in Europe and in the Islamic world until the early modern period, and as a philosopher whose major summa the Cure (al-Shifa') had a decisive impact upon European scholasticism and especially upon Thomas Aquinas (d. 1274). Primarily a metaphysical philosopher of being who was concerned with understanding the self's existence in this world in relation to its contingency, Ibn Sina's philosophy is an attempt to construct a coherent and comprehensive system that accords with the religious exigencies of Muslim culture. As such, he may be considered to be the first major Islamic philosopher. The philosophical space that he articulates for God as the Necessary Existence lays the foundation for his theories of the soul, intellect and cosmos. Furthermore, he articulated a development in the philosophical enterprise in classical Islam away from the apologetic concerns for establishing the relationship between religion and philosophy towards an attempt to make philosophical sense of key religious doctrines and even analyse and interpret the Qur'an. Recent studies have attempted to locate him within the Aristotelian and Neoplatonic traditions. His relationship with the latter is ambivalent: although accepting some keys aspects such as an emanationist cosmology, he rejected Neoplatonic epistemology and the theory of the pre-existent soul. However, his metaphysics owes much to the "Amonnian" synthesis of the later commentators on Aristotle and discussions in legal theory and kalam on meaning, signification and being. Apart from philosophy, Avicenna's other contributions lie in the fields of medicine, the natural sciences, musical theory, and mathematics. In the Islamic sciences ('ulum), he wrote a series of short commentaries on selected Qur'anic verses and chapters that reveal a trained philosopher's hermeneutical method and attempt to come to terms with revelation. He also wrote some literary allegories about whose philosophical value recent scholarship is vehemently at odds.

His influence in medieval Europe spread through the translations of his works first undertaken in Spain. In the Islamic world, his impact was immediate and led to what Michot has called "la pandémie avicennienne." When al-Ghazali led the theological attack upon the heresies of the philosophers, he singled out Avicenna, and a generation later when the Shahrastani gave an account of the doctrines of the philosophers of Islam, he relied upon the work of Avicenna, whose metaphysics he later attempted to refute in his Struggling against the Philosophers (Musari'at al-falasifa). Avicennan metaphysics became the foundation for discussions of Islamic philosophy and philosophical theology. In the early modern period in Iran, his metaphysical positions began to be displayed by a creative modification that they underwent due to the thinkers of the school of Isfahan, in particular Mulla Sadra (d. 1641).
Metaphysics is not a school or tradition but rather a sub-discipline within philosophy, as are ethics, logic and epistemology. Like many philosophical terms, "metaphysics" can be understood in a variety of ways, so any discussion of Bertrand Russell's metaphysics must select from among the various possible ways of understanding the notion, for example, as the study of being qua being, the study of the first principles or grounds of being, the study of God, and so forth. The primary sense of "metaphysics" examined here in connection to Russell is the study of the ultimate nature and constituents of reality.

Since what we know, if anything, is assumed to be real, doctrines in metaphysics typically dovetail with doctrines in epistemology. But in this article, discussion of Russell's epistemology is kept to a minimum in order to better canvas his metaphysics, beginning with his earliest adult views in 1897 and ending shortly before his death in 1970. Russell revises his conception of the nature of reality in both large and small ways throughout his career. Still, there are positions that he never abandons; particularly, the belief that reality is knowable, that it is many, that there are entities - universals - that do not exist in space and time, and that there are truths that cannot be known by direct experience or inference but are known a priori.

The word "metaphysics" sometimes is used to describe questions or doctrines that are a priori, that is, that purport to concern what transcends experience, and particularly sense-experience. Thus, a system may be called metaphysical if it contains doctrines, such as claims about the nature of the good or the nature of human reason, whose truth is supposed to be known independently of (sense) experience. Such claims have characterized philosophy from its beginnings, as has the belief that they are meaningful and valuable. However, from the modern period on, and especially in Russell's own lifetime, various schools of philosophy began to deny the legitimacy and desirability of a priori metaphysical theorizing. In fact, Russell's life begins in a period sympathetic to this traditional philosophical project, and ends in a period which is not. Concerning these "meta-metaphysical" issues (that is, doctrines not in metaphysics but about it and its feasibility), Russell remained emphatically a metaphysician throughout his life. In fact, in his later work, it is this strand more than doctrines about the nature of reality per se that justify his being considered as one of the last, great metaphysicians.
Simone de Beauvoir was one of the most preeminent French existentialist philosophers and writers. Working alongside other famous existentialists such as Jean-Paul Sartre, Albert Camus and Maurice Merleau-Ponty, de Beauvoir produced a rich corpus of writings including works on ethics, feminism, fiction, autobiography, and politics.

Beauvoir's method incorporated various political and ethical dimensions. In The Ethics of Ambiguity, she developed an existentialist ethics that condemned the "spirit of seriousness" in which people too readily identify with certain abstractions at the expense of individual freedom and responsibility. In The Second Sex, she produced an articulate attack on the fact that throughout history women have been relegated to a sphere of "immanence," and the passive acceptance of roles assigned to them by society. In The Mandarins, she fictionalized the struggles of existents trapped in ambiguous social and personal relationships at the closing of World War II. The emphasis on freedom, responsibility, and ambiguity permeate all of her works and give voice to core themes of existentialist philosophy.

Her philosophical approach is notably diverse. Her influences include French philosophy from Descartes to Bergson, the phenomenology of Edmund Husserl and Martin Heidegger, the historical materialism of Karl Marx and Friedrich Engels, and the idealism of Immanuel Kant and G. W. F Hegel. In addition to her philosophical pursuits, de Beauvoir was also an accomplished literary figure, and her novel, The Mandarins, received the prestigious Prix Goncourt award in 1954. Her most famous and influential philosophical work, The Second Sex (1949), heralded a feminist revolution and remains to this day a central text in the investigation of women's oppression and liberation.
Benedict de Spinoza was among the most important of the post-Cartesian philosophers who flourished in the second half of the 17th century. He made significant contributions in virtually every area of philosophy, and his writings reveal the influence of such divergent sources as Stoicism, Jewish Rationalism, Machiavelli, Hobbes, Descartes, and a variety of heterodox religious thinkers of his day. For this reason he is difficult to categorize, though he is usually counted, along with Descartes and Leibniz, as one of the three major Rationalists. Given Spinoza's devaluation of sense perception as a means of acquiring knowledge, his description of a purely intellectual form of cognition, and his idealization of geometry as a model for philosophy, this categorization is fair. But it should not blind us to the eclecticism of his pursuits, nor to the striking originality of his thought.

Among philosophers, Spinoza is best known for his Ethics, a monumental work that presents an ethical vision unfolding out of a monistic metaphysics in which God and Nature are identified. God is no longer the transcendent creator of the universe who rules it via providence, but Nature itself, understood as an infinite, necessary, and fully deterministic system of which humans are a part. Humans find happiness only through a rational understanding of this system and their place within it. On account of this and the many other provocative positions he advocates, Spinoza has remained an enormously controversial figure. For many, he is the harbinger of enlightened modernity who calls us to live by the guidance of reason. For others, he is the enemy of the traditions that sustain us and the denier of what is noble within us. After a review of Spinoza's life and works, this article examines the main themes of his philosophy, primarily as they are set forth in the Ethics.
Sir Francis Bacon (later Lord Verulam and the Viscount St. Albans) was an English lawyer, statesman, essayist, historian, intellectual reformer, philosopher, and champion of modern science. Early in his career he claimed "all knowledge as his province" and afterwards dedicated himself to a wholesale revaluation and re-structuring of traditional learning. To take the place of the established tradition (a miscellany of Scholasticism, humanism, and natural magic), he proposed an entirely new system based on empirical and inductive principles and the active development of new arts and inventions, a system whose ultimate goal would be the production of practical knowledge for "the use and benefit of men" and the relief of the human condition.

At the same time that he was founding and promoting this new project for the advancement of learning, Bacon was also moving up the ladder of state service. His career aspirations had been largely disappointed under Elizabeth I, but with the ascension of James his political fortunes rose. Knighted in 1603, he was then steadily promoted to a series of offices, including Solicitor General (1607), Attorney General (1613), and eventually Lord Chancellor (1618). While serving as Chancellor, he was indicted on charges of bribery and forced to leave public office. He then retired to his estate where he devoted himself full time to his continuing literary, scientific, and philosophical work. He died in 1626, leaving behind a cultural legacy that, for better or worse, includes most of the foundation for the triumph of technology and for the modern world as we currently know it.
The American author Henry David Thoreau is best known for his magnum opus Walden, or Life in the Woods (1854); second to this in popularity is his essay, "Resistance to Civil Government" (1849), which was later republished posthumously as "Civil Disobedience" (1866). His fame largely rests on his role as a literary figure exploring the wilds of the natural world, not as a philosopher.

Thoreau gravitated toward Stoic philosophy, Hindu and Buddhist insights, and European idealism and romanticism; he was an eclectic thinker weaving together various philosophies to formulate his own unique strain of American thought.

This article helps readers understand Thoreau's philosophical inclinations and his contributions to American philosophy that allow him to stand as an early innovator of American thought and literature, and it does so based on Thoreau's concept of wildness and his penchant to preserve wildness in all he encountered.

Thoreau's emphasis on the individual's encounter with wildness oriented his outlook on authorship and philosophy, education, ontology, religion, ethics, and politics. The following sections of this article will show this through evidence provided in Thoreau's literary and personal writings: his essays, books, journal entries, and letters.

In the twenty-first century, scholars have begun to take Thoreau more seriously as a philosopher. In The Senses of Walden, Stanley Cavell addresses Thoreau as an analyst of language who works against skeptical foundations. Cavell's engagement associates Thoreau with other philosophers of language, such as Ludwig Wittgenstein and J. L. Austin. Alfred I. Tauber focuses on Thoreau as a moral thinker, and the essays in Thoreau's Importance for Philosophy address Thoreau's aesthetics, environmental ethics, ideas on embodiment, moral epistemology, political ideas, and Stoic affinities. A similar philosophical emphasis can be found in The Concord Saunter, a peer-reviewed journal dedicated to the study of Thoreau's life and texts; an example is Edward F. Mooney's article examining Thoreau's wild ethics, which concludes with a summary of Thoreau's ethics of care, or more accurately, Thoreau's preservative care for all that is wild.

In the end, this emphasis on a more philosophical Thoreau makes sense. Because of Harvard College's reliance on John Locke's empirical philosophy, Thoreau extensively examined Locke's Essay on Human Understanding, and he had to study the Scottish Common Sense philosophy of Thomas Reid and Dugald Stewart. As a Transcendentalist and through his friendships with thinkers steeped in German thought, Thoreau became acquainted with German philosophers and literary figures, such as Johann Gottlieb Fichte, Johan Wolfgang von Goethe, Immanuel Kant, G. W. F. Hegel, and Friedrich von Schlegel. Finally, in Thoreau's library one could find various philosophical texts: Thomas Brown's Philosophy of the Human Mind, William Paley's The Principles of Moral and Political Philosophy, Dugald Stewart's Elements of the Philosophy of the Human Mind, and books on Nyāya and Sāṅkhya philosophies (leading schools in Hindu philosophy). Immersion in philosophy, therefore, was a crucial part of Thoreau's development as an American thinker and writer.
April 2003 -- In Atlas Shrugged, Dr. Robert Stadler finds it "outrageous" that a genius such as John Galt would have "performed a major revolution in the science of energy, just as a means to an end." "Why," Stadler demands, "did he want to waste his mind on practical appliances?" Dagny Taggart answers: "Perhaps because he liked living on earth."


That reply summarizes the attitude of the American Enlightenment, most especially the attitude of the man whose birthday we celebrate on April 13: Thomas Jefferson.

Jefferson is best known as the leading "classical liberal" in American history. As the author of the Declaration of Independence, he outlined the political principles that launched the new nation. As the framer of the Virginia Statute for Religious Liberty, he spearheaded early efforts to separate church and state. As president of the United States, he fostered the fledgling country's continental expansion, setting the stage for America to become a global power.



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Jefferson was America's first life-centered philosopher.But Jefferson was much more than a philosopher and statesman of freedom. His omnivorous appetite for the facts of nature (including human nature) is reflected in his only book, Notes on the State of Virginia , which contains exhaustive observations on every aspect of his state's natural and social environment: its flora, fauna, populations, mountains, rivers, geology, manufactures, and laws.
Even as president, Jefferson conducted botanical expeditions on which "he would climb rocks, or wade through swamps to obtain any plant he discovered or desired and seldom returned from these excursions without a variety of specimens." In his Washington residence "we see him not only with his beloved flowers, plants, books, and pet mocking-bird, but also with carpenter's tools, garden implements, maps, globes, charts, a drafting board, and scientific instruments" (I. Bernard Cohen, Science and the Founding Fathers , New York: Norton, 1995, p. 64). The East Room was cluttered with a huge fossil collection, while on the lawn frolicked young grizzly bears brought back by Lewis and Clark.

But this is not to say Thomas Jefferson was a scientific dilettante or dabbler. Far from it. After all, Jefferson is surely the only president who read Newton's Principia in Latin and could correct the leading astronomer of his day on its interpretation. But Jefferson liked to live on earth, and whenever he writes of his scientific activities, one is struck by the predominantly practical rather than contemplative cast of his mind.

Thus, what one sees at Jefferson's Monticello estate is a powerful mind bent to practical difficulties. An indefatigable gadgeteer, Jefferson filled Monticello—which he himself designed—with mechanical innovations: a complex clock in the front hallway, dumbwaiters, a revolving bookstand, a portable writing table, an invention to duplicate letters as he wrote, even a special ventilation and cooling system. The surrounding grounds serve as an elegant showcase for his interests in botany and scientific agriculture.

This very Jeffersonian attitude—that knowledge should enhance human life—was more broadly an Enlightenment attitude. Thus, in the year of Jefferson's birth, Benjamin Franklin established a "philosophical" organization with a strikingly life-centered agenda: to conduct "all philosophical Experiments that let Light into the Nature of Things, tend to increase the Power of Man over Matter, and multiply the Conveniences or Pleasures of Life." In 1769, this scientific organization became the American Philosophical Society.

From Jefferson, the society received designs for new inventions, observations on establishing weights and measures, and correspondence on everything from meteorology to fossils. He was perfectly at home discussing the heavens or mechanics with David Rittenhouse, an ingenious inventor and America's foremost astronomer; medicine and anatomy with the peerless Dr. Benjamin Rush; flora and fauna with Benjamin Smith Barton, the nation's leading botanist and anthropologist; or chemistry, physics, and electricity with the renowned Joseph Priestley.

Jefferson came to be held in such esteem by these eminent scientists that he was elected the society's president in 1796, a post they then refused to let him quit for nearly two decades. Historian Daniel J. Boorstin writes that this "was simple recognition of his leadership in American intellectual life" ( The Lost World of Thomas Jefferson , Chicago: University of Chicago Press, 1948, p. 23).

Why did this generalist command the enduring respect of specialists? Why, as Boorstin puts it, was Thomas Jefferson "the human magnet who drew them together and gave order and meaning to their discrete investigations" (p. 23)? Because Jefferson "possessed a mind more catholic than theirs and better able to see nature as a whole. Being a statesman, he persistently demanded the human implications of their science" (p. 23).

It is precisely because of his concern with the "human implications" of intellectual pursuits that Thomas Jefferson became the leader of the American Enlightenment. In countless arenas—scientific, cultural, and political—he focused the thinking of the nation's best and brightest toward the task of advancing not pure reason, but human life as an end in itself.

So, on his birthday this month, let us remember him not just as a Founding Father, architect, inventor, or scientist. Thomas Jefferson was all that, and something more. He was America's first life-centered philosopher.
Martin Heidegger is widely acknowledged to be one of the most original and important philosophers of the 20th century, while remaining one of the most controversial. His thinking has contributed to such diverse fields as phenomenology (Merleau-Ponty), existentialism (Sartre, Ortega y Gasset), hermeneutics (Gadamer, Ricoeur), political theory (Arendt, Marcuse, Habermas), psychology (Boss, Binswanger, Rollo May), and theology (Bultmann, Rahner, Tillich). His critique of traditional metaphysics and his opposition to positivism and technological world domination have been embraced by leading theorists of postmodernity (Derrida, Foucault, and Lyotard). On the other hand, his involvement in the Nazi movement has invoked a stormy debate. Although he never claimed that his philosophy was concerned with politics, political considerations have come to overshadow his philosophical work.

Heidegger's main interest was ontology or the study of being. In his fundamental treatise, Being and Time, he attempted to access being (Sein) by means of phenomenological analysis of human existence (Dasein) in respect to its temporal and historical character. After the change of his thinking ("the turn"), Heidegger placed an emphasis on language as the vehicle through which the question of being can be unfolded. He turned to the exegesis of historical texts, especially of the Presocratics, but also of Kant, Hegel, Nietzsche and Hölderlin, and to poetry, architecture, technology, and other subjects. Instead of looking for a full clarification of the meaning of being, he tried to pursue a kind of thinking which was no longer "metaphysical." He criticized the tradition of Western philosophy, which he regarded as nihilistic, for, as he claimed, the question of being as such was obliterated in it. He also stressed the nihilism of modern technological culture. By going to the Presocratic beginning of Western thought, he wanted to repeat the early Greek experience of being, so that the West could turn away from the dead end of nihilism and begin anew. His writings are notoriously difficult. Being and Time remains his most influential work.
Søren Kierkegaard is an outsider in the history of philosophy. His peculiar authorship comprises a baffling array of different narrative points of view and disciplinary subject matter, including aesthetic novels, works of psychology and Christian dogmatics, satirical prefaces, philosophical "scraps" and "postscripts," literary reviews, edifying discourses, Christian polemics, and retrospective self-interpretations. His arsenal of rhetoric includes irony, satire, parody, humor, polemic and a dialectical method of "indirect communication" - all designed to deepen the reader's subjective passionate engagement with ultimate existential issues. Like his role models Socrates and Christ, Kierkegaard takes how one lives one's life to be the prime criterion of being in the truth. Kierkegaard's closest literary and philosophical models are Plato, J.G. Hamann, G.E. Lessing, and his teacher of philosophy at the University of Copenhagen Poul Martin Møller, although Goethe, the German Romantics, Hegel, Kant and the logic of Adolf Trendelenburg are also important influences. His prime theological influence is Martin Luther, although his reactions to his Danish contemporaries N.F.S. Grundtvig and H.L. Martensen are also crucial. In addition to being dubbed "the father of existentialism," Kierkegaard is best known as a trenchant critic of Hegel and Hegelianism and for his invention or elaboration of a host of philosophical, psychological, literary and theological categories, including: anxiety, despair, melancholy, repetition, inwardness, irony, existential stages, inherited sin, teleological suspension of the ethical, Christian paradox, the absurd, reduplication, universal/exception, sacrifice, love as a duty, seduction, the demonic, and indirect communication.
Michel Foucault was a major figure in two successive waves of 20th century French thought--the structuralist wave of the 1960s and then the poststructuralist wave. By the premature end of his life, Foucault had some claim to be the most prominent living intellectual in France.

Foucault's work is transdisciplinary in nature, ranging across the concerns of the disciplines of history, sociology, psychology, and philosophy. At the first decade of the 21st century, Foucault is the author most frequently cited in the humanities in general. In the field of philosophy this is not so, despite philosophy being the primary discipline in which he was educated, and with which he ultimately identified. This relative neglect is because Foucault's conception of philosophy, in which the study of truth is inseparable from the study of history, is thoroughly at odds with the prevailing conception of what philosophy is.

Foucault's work can generally be characterized as philosophically oriented historical research; towards the end of his life, Foucault insisted that all his work was part of a single project of historically investigating the production of truth. What Foucault did across his major works was to attempt to produce an historical account of the formation of ideas, including philosophical ideas. Such an attempt was neither a simple progressive view of the history, seeing it as inexorably leading to our present understanding, nor a thoroughgoing historicism that insists on understanding ideas only by the immanent standards of the time. Rather, Foucault continually sought for a way of understanding the ideas that shape our present not only in terms of the historical function these ideas played, but also by tracing the changes in their function through history.
Arthur Schopenhauer has been dubbed the artist's philosopher on account of the inspiration his aesthetics has provided to artists of all stripes. He is also known as the philosopher of pessimism, as he articulated a worldview that challenges the value of existence. His elegant and muscular prose earn him a reputation as one the greatest German stylists. Although he never achieved the fame of such post-Kantian philosophers as Johann Gottlieb Fichte and G.W.F. Hegel in his lifetime, his thought informed the work of such luminaries as Sigmund Freud, Ludwig Wittgenstein and, most famously, Friedrich Nietzsche. He is also known as the first German philosopher to incorporate Eastern thought into his writings.

Schopenhauer's thought is iconoclastic for a number of reasons. Although he considered himself Kant's only true philosophical heir, he argued that the world was essentially irrational. Writing in the era of German Romanticism, he developed an aesthetics that was classicist in its emphasis on the eternal. When German philosophers were entrenched in the universities and immersed in the theological concerns of the time, Schopenhauer was an atheist who stayed outside the academic profession.

Schopenhauer's lack of recognition during most of his lifetime may have been due to the iconoclasm of his thought, but it was probably also partly due to his irascible and stubborn temperament. The diatribes against Hegel and Fichte peppered throughout his works provide evidence of his state of mind. Regardless of the reason Schopenhauer's philosophy was overlooked for so long, he fully deserves the prestige he enjoyed altogether too late in his life.
Voltaire (François-Marie Arouet) (November 21, 1694 - May 30, 1778) was a prolific writer, philosopher, poet and pamphletist, and the preeminent figure of the eighteenth-century French Enlightenment.

An acerbic social critic, Voltaire condemned injustice, clerical abuses, prejudice, and fanaticism. He rejected formalized religion, which he saw as superstitious and irrational, although as a deist, he believed in a supreme being. Voltaire emphasized reason, despised democracy as the rule of the mob, and believed that an enlightened monarchy, informed by the counsels of the wise, was best suited to govern.

Though Voltaire used the weapon of his wit primarily against corrupt institutions, first and foremost the Church, his attacks also aimed at revealed religion itself. His often considerable cynicism in these matters should nevertheless be seen in the context of the abysmal condition of religious life in eighteenth-century France, particularly among the educated classes. The utilitarian deism promoted by Voltaire, with its emphasis on humanistic virtues, its rejection of dogma, and its ignorance of the inner life, was the almost inevitable response to the prevailing role of the church of his time. His rejection of church authority and conventional morality also enabled Voltaire to maintain a 16-year liaison with a 27-year-old married mother of three children.

Voltaire's and other French Enlightenment philosophes' emphasis on reason above feeling would provoke a reaction during the Romantic era in the arts and literature, as well as in religious expression, notably in such theologians as Friedrich Schleiermacher. Yet the humanistic thought of Voltaire would remain an important current in the nineteenth century. Karl Marx, Charles Darwin, Friedrich Nietzsche and other thinkers would promulgate blistering critiques of religion and advance materialist explanations of human origins, history, and the inner life that would form the basis of contentious philosophical, political, and social debate in the modern era.

Above anyone else, Voltaire has also come to embody what many consider to be the typically French qualities: wit and elegance of expression. At home and abroad, the French language is sometimes referred to as the "language of Voltaire," and even the country is sometimes called the "country of Voltaire."
The German rationalist philosopher, Gottfried Wilhelm Leibniz (1646-1716), is one of the great renaissance men of Western thought. He has made significant contributions in several fields spanning the intellectual landscape, including mathematics, physics, logic, ethics, and theology. Unlike many of his contemporaries of the modern period, Leibniz does not have a canonical work that stands as his single, comprehensive piece of philosophy. Instead, in order to understand Leibniz's entire philosophical system, one must piece it together from his various essays, books, and correspondences. As a result, there are several ways to explicate Leibniz's philosophy. This article begins with his theory of truth, according to which the nature of truth consists in the connection or inclusion of a predicate in a subject.

Together with several apparently self-evident principles (such as the principle of sufficient reason, the law of contradiction, and the identity of indiscernibles), Leibniz uses his predicate-in-subject theory of truth to develop a remarkable philosophical system that provides an intricate and thorough account of reality. Ultimately, Leibniz's universe contains only God and non-composite, immaterial, soul-like entities called "monads." Strictly speaking, space, time, causation, material objects, among other things, are all illusions (at least as normally conceived). However, these illusions are well-founded on and explained by the true nature of the universe at its fundamental level. For example, Leibniz argues that things seem to cause one another because God ordained a pre-established harmony among everything in the universe. Furthermore, as consequences of his metaphysics, Leibniz proposes solutions to several deep philosophical problems, such as the problem of free will, the problem of evil, and the nature of space and time. One thus finds Leibniz developing intriguing arguments for several philosophical positions—including theism, compatibilism, and idealism.

This article is predominately concerned with this broad view of Leibniz's philosophical system and does not deal with Leibniz's work on, for example, aesthetics, political philosophy, or (except incidentally) physics. Leibniz's "mature metaphysical career" spanned over thirty years. During this period, it would be surprising if some of his basic ideas did not change, but, remarkably, the broad outline of his philosophy does remain constant.
St. Augustine is a fourth century philosopher whose groundbreaking philosophy infused Christian doctrine with Neoplatonism. He is famous for being an inimitable Catholic theologian and for his agnostic contributions to Western philosophy. He argues that skeptics have no basis for claiming to know that there is no knowledge. In a proof for existence similar to one later made famous by René Descartes, Augustine says, "[Even] If I am mistaken, I am." He is the first Western philosopher to promote what has come to be called "the argument by analogy" against solipsism: there are bodies external to mine that behave as I behave and that appear to be nourished as mine is nourished; so, by analogy, I am justified in believing that these bodies have a similar mental life to mine. Augustine believes reason to be a uniquely human cognitive capacity that comprehends deductive truths and logical necessity. Additionally, Augustine adopts a subjective view of time and says that time is nothing in reality but exists only in the human mind's apprehension of reality. He believes that time is not infinite because God "created" it.

Augustine tries to reconcile his beliefs about freewill, especially the belief that humans are morally responsible for their actions, with his belief that one's life is predestined. Though initially optimistic about the ability of humans to behave morally, at the end he is pessimistic, and thinks that original sin makes human moral behavior nearly impossible: if it were not for the rare appearance of an accidental and undeserved Grace of God, humans could not be moral. Augustine's theological discussion of freewill is relevant to a non-religious discussion regardless of the religious-specific language he uses; one can switch Augustine's "omnipotent being" and "original sin" explanation of predestination for the present day "biology" explanation of predestination; the latter tendency is apparent in modern slogans such as "biology is destiny."
John Stuart Mill (1806-1873) profoundly influenced the shape of nineteenth century British thought and political discourse. His substantial corpus of works includes texts in logic, epistemology, economics, social and political philosophy, ethics, metaphysics, religion, and current affairs. Among his most well-known and significant are A System of Logic, Principles of Political Economy, On Liberty, Utilitarianism, The Subjection of Women, Three Essays on Religion, and his Autobiography.Mill's education at the hands of his imposing father, James Mill, fostered both intellectual development (Greek at the age of three, Latin at eight) and a propensity towards reform. James Mill and Jeremy Bentham led the "Philosophic Radicals," who advocated for rationalization of the law and legal institutions, universal male suffrage, the use of economic theory in political decision-making, and a politics oriented by human happiness rather than natural rights or conservatism. In his twenties, the younger Mill felt the influence of historicism, French social thought, and Romanticism, in the form of thinkers like Coleridge, the St. Simonians, Thomas Carlyle, Goethe, and Wordsworth. This led him to begin searching for a new philosophic radicalism that would be more sensitive to the limits on reform imposed by culture and history and would emphasize the cultivation of our humanity, including the cultivation of dispositions of feeling and imagination (something he thought had been lacking in his own education).

None of Mill's major writings remain independent of his moral, political, and social agenda. Even the most abstract works, such as the System of Logic and his Examination of Sir William Hamilton's Philosophy, serve polemical purposes in the fight against the German, or a priori, school otherwise called "intuitionism." On Mill's view, intuitionism needed to be defeated in the realms of logic, mathematics, and philosophy of mind if its pernicious effects in social and political discourse were to be mitigated.

In his writings, Mill argues for a number of controversial principles. He defends radical empiricism in logic and mathematics, suggesting that basic principles of logic and mathematics are generalizations from experience rather than known a priori. The principle of utility—that "actions are right in proportion as they tend to promote happiness; wrong as they tend to produce the reverse of happiness"—was the centerpiece of his ethical philosophy. On Liberty puts forward the "harm principle" that "the only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others." In The Subjection of Women, he compares the legal status of women to the status of slaves and argues for equality in marriage and under the law.

This article provides an overview of Mill's life and major works, focusing on his key arguments and their relevant historical contexts.
In 1498, Niccolò Machiavelli began his career as an active politician in the independent city-state of Florence, engaging in diplomatic missions through France and Germany as well as Italy. After more than a decade of public service, he was driven from his post when the republic collapsed. Repeated efforts to win the confidence and approval of the new regime were unsuccessful, and Machiavelli was forced into retirement and a life of detached scholarship about the political process instead of direct participation in it. The books for which he is remembered were published only after his death.

Machiavelli originally wrote Principe. (The Prince) (1513) in hopes of securing the favor of the ruling Medici family, and he deliberately made its claims provocative. The Prince is an intensely practical guide to the exercise of raw political power over a Renaissance principality. Allowing for the unpredictable influence of fortune, Machiavelli argued that it is primarily the character or vitality or skill of the individual leader that determines the success of any state. The book surveys various bold means of acquiring and maintaining the principality and evaluates each of them solely by reference to its likelihood of augmenting the glory of the prince while serving the public interest. It is this focus on practical success by any means, even at the expense of traditional moral values, that earned Machiavelli's scheme a reputation for ruthlessness, deception, and cruelty.

His Dell'arte della guerra (The Art of War) (1520) Machiavelli explains in detail effective procedures for the acquisition, maintenance, and use of a military force. Even in his more leisurely reflections on the political process, Machiavelli often wrote in a similar vein. The Discorsi sopra la prima Deca di Tito Livio (Discourses on Livy) (1531) review the history of the Roman republic, with greater emphasis on the role of fortune and a clear admiration for republican government. Here, too, however, Machiavelli's conception of the proper application of morality to practical political life is one that judges the skill of all participants in terms of the efficacy with which they achieve noble ends. Whatever the form of government, Machiavelli held, only success and glory really matter.
Adam Smith is often identified as the father of modern capitalism. While accurate to some extent, this description is both overly simplistic and dangerously misleading. On the one hand, it is true that very few individual books have had as much impact as his An Inquiry into the Nature and Causes of the Wealth of Nations. His accounts of the division of labor and free trade, self-interest in exchange, the limits on government intervention, price, and the general structure of the market, all signify the moment when economics transitions to the "modern." On the other hand, The Wealth of Nations, as it is most often called, is not a book on economics. Its subject is "political economy," a much more expansive mixture of philosophy, political science, history, economics, anthropology, and sociology. The role of the free market and the laissez-faire structures that support it are but two components of a larger theory of human interaction and social history.

Smith was not an economist; he was a philosopher. His first book, The Theory of Moral Sentiments, sought to describe the natural principles that govern morality and the ways in which human beings come to know them. How these two books fit together is both one of the most controversial subjects in Smith scholarship and the key to understanding his arguments about the market and human activity in general. Historically, this process is made more difficult by the so-called "Adam Smith Problem," a position put forth by small numbers of committed scholars since the late nineteenth century that Smith's two books are incompatible. The argument suggests that Smith's work on ethics, which supposedly assumed altruistic human motivation, contradicts his political economy, which allegedly assumed egoism. However, most contemporary Smith scholars reject this claim as well as the description of Smith's account of human motivation it presupposes.

Smith never uses the term "capitalism;" it does not enter into widespread use until the late nineteenth century. Instead, he uses "commercial society," a phrase that emphasizes his belief that the economic is only one component of the human condition. And while, for Smith, a nation's economic "stage" helps define its social and political structures, he is also clear that the moral character of a people is the ultimate measure of their humanity. To investigate Smith's work, therefore, is to ask many of the great questions that we all struggle with today, including those that emphasize the relationship of morality and economics. Smith asks why individuals should be moral. He offers models for how people should treat themselves and others. He argues that scientific method can lead to moral discovery, and he presents a blueprint for a just society that concerns itself with its least well-off members, not just those with economic success. Adam Smith's philosophy bears little resemblance to the libertarian caricature put forth by proponents of laissez faire markets who describe humans solely as homo economicus. For Smith, the market is a mechanism of morality and social support.
Although not the first to coin the term, it is uncontroversial to suggest that the German philosopher, Edmund Husserl (1859-1938), is the "father" of the philosophical movement known as phenomenology. Phenomenology can be roughly described as the sustained attempt to describe experiences (and the "things themselves") without metaphysical and theoretical speculations. Husserl suggested that only by suspending or bracketing away the "natural attitude" could philosophy becomes its own distinctive and rigorous science, and he insisted that phenomenology is a science of consciousness rather than of empirical things. Indeed, in Husserl's hands phenomenology began as a critique of both psychologism and naturalism. Naturalism is the thesis that everything belongs to the world of nature and can be studied by the methods appropriate to studying that world (that is, the methods of the hard sciences). Husserl argued that the study of consciousness must actually be very different from the study of nature. For him, phenomenology does not proceed from the collection of large amounts of data and to a general theory beyond the data itself, as in the scientific method of induction. Rather, it aims to look at particular examples without theoretical presuppositions (such as the phenomena of intentionality, of love, of two hands touching each other, and so forth), before then discerning what is essential and necessary to these experiences. Although all of the key, subsequent phenomenologists (Heidegger, Sartre, Merleau-Ponty, Gadamer, Levinas, Derrida) have contested aspects of Husserl's characterization of phenomenology, they have nonetheless been heavily indebted to him. As such, he is arguably one of the most important and influential philosophers of the twentieth century. The key features of his work, and his understanding of the phenomenological method, are considered in what follows.
The pre-Socratic Greek philosopher Pythagoras must have been one of the world's greatest persons, but he wrote nothing, and it is hard to say how much of the doctrine we know as Pythagorean is due to the founder of the society and how much is later development. It is also hard to say how much of what we are told about the life of Pythagoras is trustworthy; for a mass of legend gathered around his name at an early date. Sometimes he is represented as a man of science, and sometimes as a preacher of mystic doctrines, and we might be tempted to regard one or other of those characters as alone historical. The truth is that there is no need to reject either of the traditional views. The union of mathematical genius and mysticism is common enough. Originally from Samos, Pythagoras founded at Kroton (in southern Italy) a society which was at once a religious community and a scientific school. Such a body was bound to excite jealousy and mistrust, and we hear of many struggles. Pythagoras himself had to flee from Kroton to Metapontion, where he died.

It is stated that he was a disciple of Anaximander, his astronomy was the natural development of Anaximander's. Also, the way in which the Pythagorean geometry developed also bears witness to its descent from that of Miletos. The great problem at this date was the duplication of the square, a problem which gave rise to the theorem of the square on the hypotenuse, commonly known still as the Pythagorean proposition (Euclid, I. 47). If we were right in assuming that Thales worked with the old 3:4:5 triangle, the connection is obvious.

Pythagoras argued that there are three kinds of men, just as there are three classes of strangers who come to the Olympic Games. The lowest consists of those who come to buy and sell, and next above them are those who come to compete. Best of all are those who simply come to look on. Men may be classified accordingly as lovers of wisdom, lovers of honor, and lovers of gain. That seems to imply the doctrine of the tripartite soul, which is also attributed to the early Pythagoreans on good authority, though it is common now to ascribe it to Plato. There are, however, clear references to it before his time, and it agrees much better with the general outlook of the Pythagoreans. The comparison of human life to a gathering like the Games was often repeated in later days. Pythagoras also taught the doctrine of Rebirth or transmigration, which we may have learned from the contemporary Orphics. Xenophanes made fun of him for pretending to recognize the voice of a departed friend in the howls of a beaten dog. Empedocles seems to be referring to him when he speaks of a man who could remember what happened ten or twenty generations before. It was on this that the doctrine of Recollection, which plays so great a part in Plato, was based. The things we perceive with the senses, Plato argues, remind us of things we knew when the soul was out of the body and could perceive reality directly.

There is more difficulty about the cosmology of Pythagoras. Hardly any school ever professed such reverence for its founder's authority as the Pythagoreans. 'The Master said so' was their watchword. On the other hand, few schools have shown so much capacity for progress and for adapting themselves to new conditions. Pythagoras started from the cosmical system of Anaximenes. Aristotle tells us that the Pythagoreans represented the world as inhaling 'air' form the boundless mass outside it, and this 'air' is identified with 'the unlimited'. When, however, we come to the process by which things are developed out of the 'unlimited', we observe a great change. We hear nothing more of 'separating out' or even of rarefaction and condensation. Instead of that we have the theory that what gives form to the Unlimited is the Limit. That is the great contribution of Pythagoras to philosophy, and we must try to understand it. Now the function of the Limit is usually illustrated from the arts of music and medicine, and we have seen how important these two arts were for Pythagoreans, so it is natural to infer that the key to its meaning is to be found in them.

It may be taken as certain that Pythagoras himself discovered the numerical ratios which determine the concordant intervals of the musical scale. Similar to musical intervals, in medicine there are opposites, such as the hot and the cold, the wet and the dry, and it is the business of the physician to produce a proper 'blend' of these in the human body. In a well-known passage of Plato's Phaedo (86 b) we are told by Simmias that the Pythagoreans held the body to be strung like an instrument to a certain pitch, hot and cold, wet and dry taking the place of high and low in music. Musical tuning and health are alike means arising from the application of Limit to the Unlimited. It was natural for Pythagoras to look for something of the same kind in the world at large. Briefly stated, the doctrine of Pythagoras was that all things are numbers. In certain fundamental cases, the early Pythagoreans represented numbers and explained their properties by means of dots arranged in certain 'figures' or patterns.
John Rawls was arguably the most important political philosopher of the twentieth century. He wrote a series of highly influential articles in the 1950s and '60s that helped refocus Anglo-American moral and political philosophy on substantive problems about what we ought to do. His first book, A Theory of Justice [TJ] (1971), revitalized the social-contract tradition, using it to articulate and defend a detailed vision of egalitarian liberalism. In Political Liberalism [PL] (1993), he recast the role of political philosophy, accommodating it to the effectively permanent "reasonable pluralism" of religious, philosophical, and other comprehensive doctrines or worldviews that characterize modern societies. He explains how philosophers can characterize public justification and the legitimate, democratic use of collective coercive power while accepting that pluralism.

Although most of this article will be devoted to TJ, the exposition of that work will take account of Political Liberalism and other later works of Rawls. TJ sets out and defends the principles of Justice as Fairness. Rawls takes the basic structure of society as his subject matter and utilitarianism as his principal opponent. Part One of TJ designs a social-contract-type thought experiment, the Original Position (OP), and argues that parties in the OP will prefer Justice as Fairness to utilitarianism and various other views. In order to understand the argument from the OP, one must pay special attention to the motivation of the parties to the OP, which is philosophically stipulated and provided with a Kantian interpretation. Part Two of TJ checks the fit between the principles of Justice as Fairness and our more concrete considered views about just institutions, thereby helping move us towards a reflective equilibrium that supports those principles. Part Three of TJ addresses the stability of a society organized around Justice as Fairness, arguing that there will be an important congruence in such a society between people's views about justice and what they value. By the time he wrote Political Liberalism, however, Rawls had decided that an inconsistency in TJ called for recasting the argument for stability. In other ways, the argument of TJ rested on important simplifications, which had the effect of setting aside questions about international justice, disability, and familial justice. Rawls turned to these "problems of extension," as he called them, at the end of his career.
George Berkeley was one of the three most famous British Empiricists. (The other two are John Locke and David Hume.) Berkeley is best known for his early works on vision (An Essay towards a New Theory of Vision, 1709) and metaphysics (A Treatise concerning the Principles of Human Knowledge, 1710; Three Dialogues between Hylas and Philonous, 1713).

Berkeley's empirical theory of vision challenged the then-standard account of distance vision, an account which requires tacit geometrical calculations. His alternative account focuses on visual and tactual objects. Berkeley argues that the visual perception of distance is explained by the correlation of ideas of sight and touch. This associative approach does away with appeals to geometrical calculation while explaining monocular vision and the moon illusion, anomalies that had plagued the geometric account.

Berkeley claimed that abstract ideas are the source of all philosophical perplexity and illusion. In his Introduction to the Principles of Human Knowledge he argued that, as Locke described abstract ideas (Berkeley considered Locke's the best account of abstraction), (1) they cannot, in fact, be formed, (2) they are not needed for communication or knowledge, and (3) they are inconsistent and therefore inconceivable.

In the Principles and the Three Dialogues Berkeley defends two metaphysical theses: idealism (the claim that everything that exists either is a mind or depends on a mind for its existence) and immaterialism (the claim that matter does not exist). His contention that all physical objects are composed of ideas is encapsulated in his motto esse is percipi (to be is to be perceived).

Although Berkeley's early works were idealistic, he says little in them regarding the nature of one's knowledge of the mind. Much of what can be gleaned regarding Berkeley's account of mind is derived from the remarks on "notions" that were added to the 1734 editions of the Principles and the Three Dialogues.

Berkeley was a priest of the Church of Ireland. In the 1720s, his religious interests came to the fore. He was named Dean of Derry in 1724. He attempted to found a college in Bermuda, spending several years in Rhode Island waiting for the British government to provide the funding it had promised. When it became clear that the funding would not be provided, he returned to London. There he published Alciphron (a defense of Christianity), criticisms of Newton's theory of infinitesimals, The Theory of Vision Vindicated, and revised editions of the Principles, and the Three Dialogues. He was named Bishop of Cloyne in 1734 and lived in Cloyne until his retirement in 1752. He was a good bishop, seeking the welfare of Protestants and Catholics alike. His Querist (1735-1737) presents arguments for the reform of the Irish economy. His last philosophical work, Siris (1744), includes a discussion of the medicinal virtues of tar water, followed by properly philosophical discussions that many scholars see as a departure from his earlier idealism.
"Critical Rationalism" is the name Karl Popper (1902-1994) gave to a modest and self-critical rationalism. He contrasted this view with "uncritical or comprehensive rationalism," the received justificationist view that only what can be proved by reason and/or experience should be accepted. Popper argued that comprehensive rationalism cannot explain how proof is possible and that it leads to inconsistencies. Critical rationalism today is the project of extending Popper's approach to all areas of thought and action. In each field the central task of critical rationalism is to replace allegedly justificatory methods with critical ones.

Section 2 explains how critical rationalism arose out of the breakdown of Popper's first justificationist attempt to account for scientific progress. Section 2 also presents Popper's first application of his non-justificationist perspective to new fields in his The Open Society and Its Enemies. Section 3 first explains Joseph Agassi's view of the critical appraisal of metaphysical theories in scientific contexts as well as his view of piecemeal rationality, and secondly portrays William Bartley's more comprehensive view of non-justificationism. Section 4 discusses Imré Lakatos's extension of critical rationalism to mathematics. Section 5 portrays Hans Albert's systematic version of critical rationalism. His perspective incorporated results of Popper, Agassi and Bartley and extended them to social and political theory. Section 6 suggests that Mario Bunge's fallibilism ─ which he developed independently of critical rationalists ─ is sufficiently close to their views to count here: he develops critical tools for achieving progress without justification in virtually all areas of thought. Section 7 discusses attempts to develop critical rationalism in new and simpler ways. These views seek to do without frameworks and methodological rules; their originators are Jagdish Hattiangadi, Gunnar Andersson, and David Miller. These theories deprive rational thought of needed steering mechanisms. Section 8 presents the reintroduction of forms of justification designed to be compatible with Popper's criticism of induction. These have been developed by Alan Musgrave, Volker Gadenne and John Watkins. Section 9 explains how Popper's emphasis on the importance of methodological rules in science has led to a critical rationalist sociology of science. The main task of this sociology of science is to examine existing rules and methods as furthering or hindering research. Section 10 calls attention to the alternative philosophical anthropology which Agassi has proposed as a framework for critical rationalism. Whereas Popper saw rationality as contrary to human nature's craving for security, Agassi sees rationality as natural, but partial and improvable. Section 11 describes how Popper's original political manifesto in The Open Society and Its Enemies has led to attempts to use his arguments to defend both right-leaning and left-leaning political theories. Section 12 returns to Popper's early researches in educational theory. His philosophy led to concerted efforts to develop a new pedagogy which emphasizes active problem solving as the best learning method. This pedagogy should promote autonomy and critical thinking. Section 13 concludes with the suggestion that the success or the failure of the project of substituting critical for allegedly justificatory methods has still to be judged.
Jeremy Bentham was an English philosopher and political radical. He is primarily known today for his moral philosophy, especially his principle of utilitarianism, which evaluates actions based upon their consequences. The relevant consequences, in particular, are the overall happiness created for everyone affected by the action. Influenced by many enlightenment thinkers, especially empiricists such as John Locke and David Hume, Bentham developed an ethical theory grounded in a largely empiricist account of human nature. He famously held a hedonistic account of both motivation and value according to which what is fundamentally valuable and what ultimately motivates us is pleasure and pain. Happiness, according to Bentham, is thus a matter of experiencing pleasure and lack of pain.

Although he never practiced law, Bentham did write a great deal of philosophy of law, spending most of his life critiquing the existing law and strongly advocating legal reform. Throughout his work, he critiques various natural accounts of law which claim, for example, that liberty, rights, and so on exist independent of government. In this way, Bentham arguably developed an early form of what is now often called "legal positivism." Beyond such critiques, he ultimately maintained that putting his moral theory into consistent practice would yield results in legal theory by providing justification for social, political, and legal institutions.

Bentham's influence was minor during his life. But his impact was greater in later years as his ideas were carried on by followers such as John Stuart Mill, John Austin, and other consequentialists.
W. V. O. Quine (1908-2000) did not conceive of philosophy as an activity separate from the general province of empirical science. His interest in science is not best described as a philosophy of science but as a set of reflections on the nature of science that is pursued with the same empirical spirit that animates scientific inquiry. Quine's philosophy should then be seen as a systematic attempt to understand science from within the resources of science itself. This project investigates both the epistemological and ontological dimensions of scientific theorizing. Quine's epistemological concern is to examine our successful acquisition of scientific theories, while his ontological interests focus on the further logical regimentation of that theory. He thus advocates what is more famously known as 'naturalized epistemology', which consists of his attempt to provide an improved scientific explanation of how we have developed elaborate scientific theories on the basis of meager sensory input. Quine further argues that the most general features of reality can be examined through the use of formal logic by clarifying what objects we must acknowledge as real given our acceptance of an overarching systematic view of the world. In pursuing these issues, Quine reformulates and thus transforms these philosophical concerns according to those standards of clarity, empirical adequacy, and utility that he takes as central to the explanatory power of empirical science. While few philosophers have adopted Quine's strict standards or accepted the details of his respective positions, the general empirical reconfiguration of philosophy and philosophy of science recommended by his naturalism has been very influential. This article provides an overview of Quine's naturalistic conception of philosophy, and elaborates on its examination of the epistemological and ontological elements of scientific practice.
William James is considered by many to be the most insightful and stimulating of American philosophers, as well as the second of the three great pragmatists (the middle link between Charles Sanders Peirce and John Dewey). As a professor of psychology and of philosophy at Harvard University, he became the most famous living American psychologist and later the most famous living American philosopher of his time. Avoiding the logically tight systems typical of European rationalists, such as the German idealists, he cobbled together a psychology rich in philosophical implications and a philosophy enriched by his psychological expertise. More specifically, his theory of the self and his view of human belief as oriented towards conscious action raised issues that required him to turn to philosophy. There he developed his pragmatic epistemology, which considers the meaning of ideas and the truth of beliefs not abstractly, but in terms of the practical difference they can make in people's lives. He explored the implications of this theory in areas of religious belief, metaphysics, human freedom and moral values, and social philosophy. His contributions in these areas included critiques of long-standing philosophical positions on such issues as freedom vs. determinism, correspondence vs. coherence, and dualism vs. materialism, as well as a thorough analysis of a phenomenological understanding of the self and consciousness, a "forward-looking" conception of truth (based on validation and revisable experience), a thorough-going metaphysical pluralism, and a commitment to a full view of agency in connection with communal and social concerns. Thus he created one of the last great philosophical systems in Western thought, even if he did not live quite long enough to complete every aspect of it. The combination of his provocative ideas and his engaging writing style has contributed to the enduring impact of his work.
Hypatia, (born c. 355 ce—died March 415, Alexandria), Egyptian mathematician, astronomer, and philosopher who lived in a very turbulent era in Alexandria's history. She is the earliest female mathematician of whose life and work reasonably detailed knowledge exists.

Hypatia was the daughter of Theon of Alexandria, himself a mathematician and astronomer and the last attested member of the Alexandrian Museum. Theon is best remembered for the part he played in the preservation of Euclid's Elements, but he also wrote extensively, commenting on Ptolemy's Almagest and Handy Tables. Hypatia continued his program, which was essentially a determined effort to preserve the Greek mathematical and astronomical heritage in extremely difficult times. She is credited with commentaries on Apollonius of Perga's Conics (geometry) and Diophantus of Alexandria's Arithmetic (number theory), as well as an astronomical table (possibly a revised version of Book III of her father's commentary on the Almagest). These works, the only ones she is listed as having written, have been lost, although there have been attempts to reconstruct aspects of them. In producing her commentaries on Apollonius and Diophantus, she was pushing the program initiated by her father into more recent and more difficult areas.

She was, in her time, the world's leading mathematician and astronomer, the only woman for whom such claim can be made. She was also a popular teacher and lecturer on philosophical topics of a less-specialist nature, attracting many loyal students and large audiences. Her philosophy was Neoplatonist and was thus seen as "pagan" at a time of bitter religious conflict between Christians (both orthodox and "heretical"), Jews, and pagans. Her Neoplatonism was concerned with the approach to the One, an underlying reality partially accessible via the human power of abstraction from the Platonic forms, themselves abstractions from the world of everyday reality. Her philosophy also led her to embrace a life of dedicated virginity.



Hypatia of Alexandria: murder [Credit: © Photos.com/Thinkstock]
An early manifestation of the religious divide of the time was the razing of the Serapeum, the temple of the Greco-Egyptian god Serapis, by Theophilus, Alexandria's bishop until his death in 412 ce. This event was perhaps the final end of the great Library of Alexandria, since the Serapeum may have contained some of the Library's books. Theophilus, however, was friendly with Synesius, an ardent admirer and pupil of Hypatia, so she was not herself affected by this development but was permitted to pursue her intellectual endeavours unimpeded. With the deaths of Synesius and Theophilus and the accession of Cyril to the bishopric of Alexandria, however, this climate of tolerance lapsed, and shortly afterward Hypatia became the victim of a particularly brutal murder at the hands of a gang of Christian zealots. It remains a matter of vigorous debate how much the guilt of this atrocity is Cyril's, but the affair made Hypatia a powerful feminist symbol and a figure of affirmation for intellectual endeavour in the face of ignorant prejudice. Her intellectual accomplishments alone were quite sufficient to merit the preservation and respect of her name, but sadly, the manner of her death added to it an even greater emphasis.
Saul Kripke, in full Saul Aaron Kripke (born Nov. 13, 1940, Bay Shore, Long Island, N.Y., U.S.), American logician and philosopher who from the 1960s was one of the most powerful thinkers in Anglo-American philosophy (see analytic philosophy).

Kripke began his important work on the semantics of modal logic (the logic of modal notions such as necessity and possibility) while he was still a high-school student in Omaha, Neb. A groundbreaking paper from this period, "A Completeness Theorem for Modal Logic," was published in the Journal of Symbolic Logic in 1959, during Kripke's freshman year at Harvard University. In 1962 he graduated from Harvard with the only nonhonorary degree he ever received, a B.S. in mathematics. He remained at Harvard until 1968, first as a member of the Harvard Society of Fellows and then as a lecturer. During these years he continued a series of publications extending his original results in modal logic; he also published important papers in intuitionistic logic (the logic underlying the mathematical intuitionism of L.E.J. Brouwer), set theory, and the theory of transfinite recursion (see recursive function). Kripke taught logic and philosophy at Rockefeller University from 1968 to 1976 and at Princeton University, as McCosh Professor of Philosophy, from 1976 until his retirement in 1998. He delivered the prestigious John Locke Lectures at the University of Oxford in 1973 and received the Rolf Schock Prize in logic and philosophy, awarded by the Royal Swedish Academy of Sciences, in 2001. In 2003 he was appointed distinguished professor at the City University of New York (CUNY).


Naming and Necessity

Kripke's most important philosophical publication, Naming and Necessity (1980), based on transcripts of three lectures he delivered at Princeton in 1970, changed the course of analytic philosophy. It provided the first cogent account of necessity and possibility as metaphysical concepts, and it distinguished both concepts from the epistemological notions of a posteriori knowledge and a priori knowledge (knowledge acquired through experience and knowledge independent of experience, respectively) and from the linguistic notions of analytic truth and synthetic truth, or truth by virtue of meaning and truth by virtue of fact (see analytic proposition). In the course of making these distinctions, Kripke revived the ancient doctrine of essentialism, according to which objects possess certain properties necessarily—without them the objects would not exist at all. On the basis of this doctrine and revolutionary new ideas about the meaning and reference of proper names and of common nouns denoting "natural kinds" (such as heat, water, and tiger), he argued forcefully that some propositions are necessarily true but knowable only a posteriori—e.g., "Water is H2O" and "Heat is mean molecular kinetic energy"—and that some propositions are contingently true (true in some circumstances but not others) but knowable a priori. These arguments overturned the conventional view, inherited from Immanuel Kant (1720-1804), that identified all a priori propositions as necessary and all a posteriori propositions as contingent. Naming and Necessity also had far-reaching implications regarding the question of whether linguistic meaning and the contents of beliefs and other mental states are partly constituted by social and environmental facts external to the individual. According to Kripke's causal theory of reference, for example, the referent of a given use of a proper name, such as Aristotle, is transmitted through an indefinitely long series of earlier uses; this series constitutes a causal-historical chain that is traceable, in principle, to an original, or "baptismal," application. Kripke's view posed a serious challenge to the prevailing "description" theory, which held that the referent of a name is the individual who is picked out by an associated definite description, such as (in the case of Aristotle) the teacher of Alexander the Great. Finally, Kripke's work contributed greatly to the decline of ordinary language philosophy and related schools, which held that philosophy is nothing more than the logical analysis of language.


Truth

In 1975-76 Kripke published important work on the notion of truth and the liar paradox (which involves sentences that say of themselves that they are not true). According to the then-dominant approach, developed by the Polish logician Alfred Tarski, the liar paradox requires giving up the view that a natural language such as English contains a single truth predicate. Instead, there is a hierarchy of predicates truen for each integer n. The range of each predicate is restricted to that subpart of the language whose sentences contain either no truth predicate at all or truth predicates of a level less than n. Since it follows from this that sentences assessing their own truth or untruth cannot be formulated, inconsistency is avoided, though at the cost of a certain loss of expressive power. Kripke developed a nonhierarchical framework that retained much of this expressive power without surrendering too many of the advantages of Tarski's theory. Kripke's approach relied on certain previously known conditions under which languages can contain their own truth predicates and on his own intuitive conception of true as a predicate that is only partially defined—i.e., defined by rules that determine a class of positive cases to which the predicate applies, a class of negative cases to which it does not apply, and a class of cases for which no result can be reached. Although certain problems arising from the liar paradox remained recalcitrant, Kripke's framework succeeded in inspiring and guiding much subsequent work.


Meaning and skepticism

In later years Kripke wrote several influential papers on linguistic meaning and language use. "Speaker's Reference and Semantic Reference" (1977), for example, explained discrepancies between what the rules of a language determine the referent of a term to be and what speakers use the term to refer to in particular cases. "A Puzzle About Belief" (1979) generated surprising and paradoxical conclusions from seemingly innocent applications of the principles employed in reporting the beliefs of others, and it derived cautionary lessons about attempts to infer facts about linguistic meaning from analyses of belief-reporting sentences. In Wittgenstein: On Rules and Private Language (1982), Kripke used considerations originating in the Philosophical Investigations (1953) of Ludwig Wittgenstein to raise skeptical questions about whether knowledge of linguistic meaning can be reduced to rule following, or indeed to any objective facts about speakers. Although Kripke himself drew no conclusion on this point, his discussion was widely interpreted as a serious challenge to attempts to explain meaning in purely naturalistic terms.

Although a prolific thinker and problem solver, Kripke chose to publish relatively few of his works. Nevertheless, some of his unpublished papers—on recursion theory, truth, the nature of logic, personal identity, the ontological nature of numbers, colour and colour terms, presupposition, and various paradoxes—have been influential through lectures, seminars, and informal circulation among colleagues and students.
Abu al-Walid Muhammad ibn Ahmad ibn Rushd, better known in the Latin West as Averroes, lived during a unique period in Western intellectual history, in which interest in philosophy and theology was waning in the Muslim world and just beginning to flourish in Latin Christendom. Just fifteen years before his birth, the great critic of Islamic philosophy, al-Ghazzali (1058-1111), had died after striking a blow against Muslim Neoplatonic philosophy, particularly against the work of the philosopher Ibn Sina (Avicenna). From such bleak circumstances emerged the Spanish-Muslim philosophers, of which the jurist and physician Ibn Rushd came to be regarded as the final and most influential Muslim philosopher, especially to those who inherited the tradition of Muslim philosophy in the West.

His influential commentaries and unique interpretations on Aristotle revived Western scholarly interest in ancient Greek philosophy, whose works for the most part had been neglected since the sixth century. He critically examined the alleged tension between philosophy and religion in the Decisive Treatise, and he challenged the anti-philosophical sentiments within the Sunni tradition sparked by al-Ghazzali. This critique ignited a similar re-examination within the Christian tradition, influencing a line of scholars who would come to be identified as the "Averroists."

Ibn Rushd contended that the claim of many Muslim theologians that philosophers were outside the fold of Islam had no base in scripture. His novel exegesis of seminal Quranic verses made the case for three valid "paths" of arriving at religious truths, and that philosophy was one if not the best of them, therefore its study should not be prohibited. He also challenged Asharite, Mutazilite, Sufi, and "literalist" conceptions of God's attributes and actions, noting the philosophical issues that arise out of their notions of occasionalism, divine speech, and explanations of the origin of the world. Ibn Rushd strived to demonstrate that without engaging religion critically and philosophically, deeper meanings of the tradition can be lost, ultimately leading to deviant and incorrect understandings of the divine.
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