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Arts and Humanities
Terms in this set (21)
What is philosophical scepticism?
The thesis that we can not know anything about a certain domain.
What is scepticism about the external world?
The thesis that we can not know anything about the external world.
How does Descartes call into doubt knowledge about the external world?
He reflects upon the sources of our knowledge of the external world - as opposed to enumerating all the things we think we know.
What is the argument for scepticism about the external world from sensory unreliability?
P1 - everything we believe about the world is based on sensory perception.
P2 - for sensory perception to be a source of knowledge, it must always be reliable.
P3 - sensory perception is not always reliable.
C1 - sensory perception is not a source of knowledge.
C2 - we do not know anything about the external world.
What is an example of unreliable sensory perception?
Illusion of a straight rod looking bent when submerged in water; objects looking smaller when they are further away.
What is the main issue with the argument for scepticism about the external world from sensory unreliability?
Premise 2: rare cases of failure should not cause us to abandon all trust in a process. For example, we know that vision is bad at long distances, but this doesn't mean we can never gain knowledge through vision.
How can the argument for scepticism about the external world from sensory unreliability be adjusted to allow us to doubt all knowledge from sensory perception?
If we use a representative case in which our senses are functioning very reliably and can doubt we have knowledge even here, then we can show that we can not gain knowledge of the external world through any instances of sensory perception.
If the best possible case of sensory perception fails to allow us to gain knowledge, then all cases of sensory perception fail to allow us to gain knowledge.
How can we doubt even the most reliable case of sensory perception?
By postulating that we are dreaming.
What is the argument for scepticism about the external world from dreaming?
P1 - in order to know something about the external world, I must be able to know that I am not dreaming that thing.
P2 - I cannot know that I am not dreaming.
C - I cannot know anything about the external world.
Can I know that I am not dreaming?
No; any type of test which concludes that we are not dreaming cannot be accepted - because there is the possibility that the result (a part of the external world) itself is dreamt.
What general principle does the first premise of the dreaming argument for scepticism use?
In order to know P, I must rule out every possibility that is incompatible with my knowing that P.
Is it true that in order to know P, I must rule out every possibility that is incompatible with my knowing that P?
Seems too demanding; in order to know I am, say, looking at a bird I don't rule out every single incompatible possibility with my knowing that P. For example, that I am being hypnotised, or under a curse, or hallucinating, and so. This would take almost infinitely long, so the principle premise (1) relies on cannot be viably asserted. As such premise (1) should not be accepted.
How can the general principle of premise one of the dreaming argument for scepticism be adjusted to overcome the issue of it being too over-demanding? (ie. so the dreaming argument still stands)
In order to know P, I must be able to rule out possibilities that I know to be incompatible with my knowing that P; incpompatibilies that I am aware could currently alter my mental state.
I know that dreaming is incompatible with my knowing that P; it would alter my mental state. I cannot rule out that I am dreaming, so the conclusion still stands with this adjusted premise.
What is the 'reliabilist' response to scepticism?
'Reliabilism': knowledge is a true belief produced by a reliable mechanism. Our senses are generally reliable, so we have knowledge of the external world.
What is the issue with the 'reliabilist' response to scepticism?
I don't have a reliable reason to know the reliable causal process works. Say vision is reliable. How do I know that vision is reliable? I don't. There is no independent way to know that I know when reliabilism is asserted. This creates a larger problem, so the theory should be rejected.
What is the 'contextualism' response to scepticism?
Contextualism: There can be two types of knowledge.
(i) Real knowledge; with complete certainty.
(ii) Ordinary knowledge; less certain knowledge but one that is still practical.
The standards for knowledge shift in different contexts (between epistemology and practical settings).
What is Moore's proof for the external world?
P1 - I know p (eg. that there are two hands in front of me)
P2 - If I know that p is true, then scepticism about the external world is false.
C - Therefore, scepticism about the external world is false.
(Valid, modus ponens)
What are the two issues with Moore's proof for the external world?
(i) Premise one is not justified.
(ii) Moore uses an epistemic closure principle which is false.
Why is Moore's first premise not justified?
It begs the question; Moore does not demonstrate how this premise is true, he just asserts it.
Moore seems to miss the point of scepticism, asserting that if he doesn't know that his hands are in front of him, he might as well suggest he does not know that he is standing up and talking in a lecture. Yet, this is the point of scepticism itself!
It seems Moore may be falling into a contextualist view.
What are the two types of epistemic closure?
(i) Knowledge is closed under entailment: If p entails q, then if I know p, I could know q.
(ii) Strong closure: If I know that p entails q, then if I know p, then I do know that q.
How does Moore use an epistemic closure principle which is false?
We cannot know that scepticism is false by virtue of simply knowing an everyday fact.
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