How can we help?

You can also find more resources in our Help Center.

IntroLogic01-18

STUDY
PLAY
logic
the science and art of reasoning well
term
a concept that can be expressed precisely
Law of the Excluded Middle
Any statement that is either true or false
Law of Identity
If a statement is true, then it is true.
Law of Non-contradiction
When a statement cannot be both true and false.
Formal Logic
Deals withe the proper modes of reasoning.
Informal Logic
Deals with operations of thinking that are indirectly related to reasoning.
Induction (Inductive Reasoning)
Is reasoning with probability from examples or experiences to heneral rules
Deduction (Deductive Reasoning)
Is reasoning with certainty from premises to conclusions.
ambiguous
When a word has more than 1 definition.
vague
When a word is one whose extent is unclear.
Genus of a term
That is more general, broad or abstract than the original term and includes it.
Species of a Term
A term that is more specific, narrow, or concrete than the orginal term and is included by it.
Extension
The sum of all the individual objects described by it.
Intension
The sum of all the common attributes denoted by the term.
Definition
A statement that gives the meaning of a term.
Lexical Definition
Shows relationships or reduces ambiguity by providing a single established meaning of a term.
Stipulative Definition
A definition which supplies the meaning of a new term.
Persuasive Definition
Defined to influence the attitudes and emotions of the audience.
Precising Definition
Definition which reduces the vagueness of a term in a given situation.
Theoretical Definition
The word may be familiar, but not understood. For ex.: H2O for water.
statement
a sentence which is either true or false
self-supporting statement
a statement whose truth value can be determined from the statement itself
tautology
a statement which is always true because of its logical structure
self-contradiction
a statement that is false due to its logical structure
supported statement
a statement whose truth value depends on evidence or information from outside itself
consistent statements
they can both be true at the same time
implication (statements related by)
two statements are related by implication if the truth of one requires the truth of the other
logically equivalent statements
if they imply one another
independent statements
the truth or falsity of one has no effect on the truth or falsity of the other
disagreement
when there appears to be inconsistency
real disagreement
an actual inconsistancy between two statements: they cannot both be true at the same time
apparent disagreement
difference of opinion or perception
verbal disagreement
a misunderstanding due to differing definitions for one or more words
subject
the term being described, or about which something is asserted
predicate
is the term that describes or asserts something about the subject
quantity of a statement
the scope of its claim about the extension of the subject: universal (entire extension) or particular (partial)
quality of a statement
is the positive or negative nature of its claim about the subject: affirmative (asserts something) or negative (denies something)
3 ways to determine truth value of a supported statement
authority; experience; deduction
Requirements of Standard Categorical Form
1. Statements must begin w/ all, no, or some. 2. Verb must be a verb of being: is, are, etc. 3. Both subject and predicate must be a noun or a noun phrase.
square of opposition
a diagram of the basic relationships between statements with the same subject and predicate
contradiction
two statements are in contradiction if and only if they always have opposite truth values
contrary
two statements are contrary if and only if they can both be false but cannot both be true
subcontraries
two statements are subcontraries if and only if both can be true but both cannot be false
subimplication
the relationship between a universal and particular statement of the same quality, in which the truth of the universal necessitates the truth of the particular
superimplication
the relationship between a universal and particular statement of the same quality, in which the falsity of the particular necessitates the falsity of the universal.