Philosophy 100 - PowerPoint PPT Presentation

1 / 75

About This Presentation

Title:

Philosophy 100

Description:

Some basic logic: Modus Ponens (1) If we have eggs, then Jim went to the ... something's being a zebra implies that it is not a mule [...] cleverly disguised ... – PowerPoint PPT presentation

Number of Views:41

Avg rating:3.0/5.0

Slides: 76

Provided by: del5212

Category:

more less

Transcript and Presenter's Notes

Title: Philosophy 100

1
Philosophy 100

Lecture Skepticism

Some background logic

3
The Logic of Skepticism

Some basic logic Modus Ponens
(1) If we have eggs, then Jim went to the store.
(2) We have eggs.
(3) ? Jim went to the store.

4
The Logic of Skepticism

Some basic logic Modus Ponens
(1) If we have eggs, then Jim went to the store.
(2) We have eggs.
(3) ? Jim went to the store.
- Logic deals with the form, not the content of
arguments. So, to consider only the form of this
argument, we will cut the content out.

5
The Logic of Skepticism

Some basic logic Modus Ponens
(A)
(1) If we have eggs, then Jim went to the store.
(2) We have eggs. (A)
(3) ? Jim went to the store.

6
The Logic of Skepticism

Some basic logic Modus Ponens
(1) If we (A)veeggs, then Jim went to the store.
(2) (A)
(3) ? Jim went to the store.

7
The Logic of Skepticism

Some basic logic Modus Ponens
(B)
(1) If we (A)veeggs, then Jim went to the store.
(2) (A)
(3) ? Jim went to the store. (B)

8
The Logic of Skepticism

Some basic logic Modus Ponens
(1) If we (A)veeggs, then Jim (B)t to the store
(2) (A)
(3) ? (B)

9
The Logic of Skepticism

Some basic logic Modus Ponens
(1) If we have eggs, then Jim went to the store.
(2) We have eggs.
(3) ? Jim went to the store.

10
The Logic of Skepticism

Some basic logic Modus Tollens
(1) If we have eggs, then Jim went to the store.
(2) Jim didnt go to the store.
(3) ? We dont have eggs.

11
The Logic of Skepticism

Some basic logic Modus Tollens
(1) If we (A)veeggs, then Jim (B)t to the store
(2) (B)
(3) ? (A)

12
The Logic of Skepticism

Some basic logic Modus Tollens
(1) If A, then Bt to the store
(2) B
(3) ? A

13
The Logic of Skepticism

Some basic logic Modus Tollens
(1) If A, then Bt to the store
(2) B
(3) ? A
Skepticism in contemporary philosophy is usually
put forth as a Modus Tollens argument.

Descartes Argument for Skepticism

15
Skepticism

In contemporary terminology, the ground for
doubt proposed by Descartes can be put like this
U My epistemic equipment is untrustworthy.
The Cartesian-style argument for Academic
Skepticism can now be put like this
(1) If I know that p, then there are no genuine
grounds for doubting that p.
(2) U is a genuine ground for doubting that p.
(3) Therefore, I do not know that p.
(SEP Skepticism)

16
Skepticism

In contemporary terminology, the ground for
doubt proposed by Descartes can be put like this
U My epistemic equipment is untrustworthy.
The Cartesian-style argument for Academic
Skepticism can now be put like this
(1) If I know that p, then there are no genuine
grounds for doubting that p.
(2) U is a genuine ground for doubting that p.
(3) Therefore, I do not know that p.
(SEP Skepticism)

The Contemporary Argument for Skepticism

18
Skepticism

O Ordinary Beliefs
(e.g. I have two hands, Class begins at
1030, Blackholes exist)
S Skeptical Hypotheses

19
Skepticism

O Ordinary Beliefs
(e.g. I have two hands, Class begins at
1030, Blackholes exist)
S Skeptical Hypotheses
(e.g. Dreams, Brain-in-a-vat, Subjective
Contributions)

20
Skepticism

O Ordinary Beliefs
(e.g. I have two hands, Class begins at
1030, Blackholes exist)
S Skeptical Hypotheses

21
Skepticism

O Ordinary Beliefs
S Skeptical Hypotheses

22
Skepticism

O Ordinary Beliefs
S Skeptical Hypotheses
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

The Arguments Against Skepticism

24
The Arguments Against Skepticism

Reject The Principle of Closure
Contextualism
Invariantism
Verificationism
Hilary Putnam
G.E. Moore
Wittgenstein
Paper Doubt

25
The Arguments Against Skepticism

Reject The Principle of Closure
Contextualism
Invariantism
Verificationism
Hilary Putnam
G.E. Moore
Wittgenstein
Paper Doubt

26
Skepticism

(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

27
Skepticism

Closure If person P knows p and p entails
q, then P knows q.
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

28
Skepticism

Closure If person P knows p and p entails
q, then P knows q.
Reject Closure?
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

29
Skepticism

Closure If person P knows p and p entails
q, then P knows q.
Reject Closure?
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

30
The Arguments Against Skepticism

Reject The Principle of Closure
Contextualism
Invariantism
Verificationism
Hilary Putnam
G.E. Moore
Wittgenstein
Paper Doubt

31
Skepticism

(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

32
Skepticism

Contextualism Knows is an indexical term.
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

33
Skepticism

Contextualism Knows is an indexical term.
Indexical (e.g. I or small)
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

34
Skepticism

Contextualism Knows is an indexical term.
Know-1 Ordinary Contexts
Know-2 Philosophy Class
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

35
Skepticism

Contextualism Knows is an indexical term.
Know-1 Ordinary Contexts
Know-2 Philosophy Class
(1) If person P knows-2 O, then person P knows-2
S.
(2) Person P does not know-2 S.
(3) ? Person P does not know-1 O.

36
Skepticism

something's being a zebra implies that it
is not a mule cleverly disguised by the zoo
authorities to look like a zebra. Do you know
that these animals are not mules cleverly
disguised? If you are tempted to say "Yes" to
this question, think a moment about what reasons
you have, what evidence you can produce in favor
of this claim. The evidence you had for thinking
them zebras has been effectively neutralized,
since it does not count toward their not being
mules cleverly disguised to look like zebras.
(Dretske 1970, 1015-1016)

37
The Arguments Against Skepticism

Reject The Principle of Closure
Contextualism
Invariantism
Verificationism
Hilary Putnam
G.E. Moore
Wittgenstein
Paper Doubt

38
Skepticism

(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

39
Skepticism

Invariantism Knows is interest relative.
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

40
Skepticism

Invariantism Knows is interest relative.
Know-1 Low-risk contexts
Know-2 High-risk contexts
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

41
Skepticism

Invariantism Knows is interest relative.
Know-1 Low-risk contexts
Know-2 High-risk contexts

42
Skepticism

Invariantism Knows is interest relative.
Know-1 Low-risk contexts
Know-2 High-risk contexts
Bank cases (1) High-risk bank case,
(2) Low-risk bank case.

43
Skepticism

Invariantism Knows is interest relative.
Know-1 Low-risk contexts
Know-2 High-risk contexts

44
Skepticism

Invariantism Knows is interest relative.
Know-1 Low-risk contexts
Know-2 High-risk contexts
(1) If person P knows O, then person P knows S.
(2) Person P does not know S.
(3) ? Person P does not know O.

45
Skepticism

Invariantism Knows is interest relative.
Know-1 Low-risk contexts
Know-2 High-risk contexts
(1) If person P knows-2 O, then person P knows-2
S.
(2) Person P does not know-2 S.
(3) ? Person P does not know-1 O.

46
The Arguments Against Skepticism

Reject The Principle of Closure
Contextualism
Invariantism
Verificationism
Hilary Putnam
G.E. Moore
Wittgenstein
Paper Doubt

47
(No Transcript)
48
Where?
49
I dont see it.
50
Well then Ill just walk over there and feel it.
51
Then lets group up and corner him.
52
And so on
53
Philosophy of Science