Title: Knowledge and Mind
1Knowledge and Mind
2Testimony Two questions
- 1. What is the nature of testimony?
- 2. Can testimonial beliefs be justified?
31. The Nature of Testimony
- Elucidate the nature of testimony by asking
several questions - Does testimony imply truth? Can you testify
something if what you say is false? - Does testimony imply that you believe that what
you testify is true? Can you testify something if
you believe that what you say is false (even
though it might in fact be true)?
42. The Nature of Testimony
- Does testimony imply the intention to testify?
- John is sitting in his room. In the next room,
his neighbour Jill is talking to herself again.
She says I really hate my boyfriend. She did
not have the intention to communicate this
information to John. Did she testify that she
hates her boyfriend? - Answer no.
- Reason no intention to communicate information.
53. The Nature of Testimony
- Does testimony imply the intention to testify?
- John is sitting in his room. In the next room,
his neighbour Jill is talking to her friend Anne.
She says I really hate my boyfriend. She did
have the intention to communicate this
information to Anne. John happens to overhear the
conversation. Did Jill testifying that she hates
her boyfriend to John? - Answer no.
- Reason no intention to communicate information
to John.
6Justification of testimonial-based beliefs
- Two views
- Reductionism, and
- non-reductionism.
7The Nature of Testimony
- Perhaps difficult to answer because testimony
is a technical term?
8Reductionism
- For a testimony-based belief to be justified,
there must be additional evidence to support the
belief. The testimony all by itself is not
sufficient to give justification to the belief
based on that testimony.
9Two versions of reductionism
- Global reductionism in order for testimony-based
belief B to be justified, the hearer must have
reasons to think that testimony in general is
reliable.
10Two problems for global reductionism
- 1. Children would have to wait with accepting
testimony until they have been able to check for
a wide-ranging samples of testimony that these
samples are based on a reliable source. - 2. Unclear that there is a fact of the matter
regarding whether testimony is reliable in
general. There are many different types of
testimony.
11Local reductionism
- This is the view that in order for a
testimony-based belief to be justified, the
subject must only have reasons to think that the
particular instance of testimony is reliable.
12Counterexample to local reductionism
- Fred has excellent reason to believe that Helen
is a highly reliable source of information.
Yesterday, Helen told Fred that Pauline is a
highly trustworthy person when it comes to
information regarding wild birds. Pauline told
Fred that albatrosses, not condors, have the
largest wingspan among birds. Fred believed her
testimony. In that case, however, Pauline was
completely wrong. In fact, Pauline is a very
incompetent and insincere speaker. (from Lackey
2006) - Is Fred justified?
- Intuitively no
- According to local reductionism, however, he is!
13Non-reductionism
- The view that a testimony-based belief can be
justified even though there is no additional
evidence.
14Counterexample to non-reductionsim
- Sam is a human being. One day, he walks through
the forest and sees something drop a book. The
individuals appearance enables Sam to identify it
as an alien from another planet. Sam picks up the
book, notices that it is a diary, and reads the
tigers have eater some of the inhabitants of
Earth. This information is correct. (from
Jennifer Lackey 2006) - Does Sams testimony-based belief have
justification? - Yes, according to non-reductionism.
- No, according to our intuitions. It seems
irrational for Sam to believe this. It may well
be that these aliens are always insincere and
deceptive when trying to testify to others.
15Next week
16Tuesday, April 24th 2007
- Perception and Radical Scepticism
17Perception
- One of the most important sources of knowledge.
- Testimony even presupposes perception.
18The problem
- The way things look isnt always the way things
are. - Example a straight stick will look bend when
placed underwater. - Example you look at a red wall. But the wall is
actually white but illuminated by a red light. - So is perception a reliable guide to the nature
of reality? Should we trust perception?
19Radical scepticism and perception
- Suppose you look at your hand. You perceive what
you think is your hand. And you form the belief
that you are seeing your hand. - But do you know that you have hands on the basis
of perception? - The sceptic will answer no!
20Radical scepticism
- It might be the case that you are a
brain-in-a-vat (BIV) or that you are deceived by
an evil demon. - The deception is such that it provides you with
exactly the same experiences as you would have
had were you not deceived. - So there is no way to distinguish between being
deceived into believing that you are perceiving a
hand, and genuinely believing that you are
perceiving a hand.
21Evidence underdetermined
- So the problem is that the evidence we have for
perceptual beliefs is underdetermined. The
evidence of seeing hands can both be explained by
us having hands and by our being deceived into
perceiving hands.
22Sceptical paradox
- All this is formalized in the sceptical paradox
- 1. K BIV
- 2. K BIV ? -K hands
- 3. K hands
23Paradox?
- Because
- (i) intuitive premises
- (ii) sound reasoning
- (iii) counterintuitive conclusion
24Ways out of the paradox
- 1. deny premise 1
- 2. deny premise 2
- 3. accept the conclusion
25Deny premise 1
- Mooreanism.
- We can know that we are not BIVs because we know
that we have hands - Reverses the sceptical argument, from modus
ponens to modus tollens
26- Khands
- Khands --gt K-BIV
- Hence, K-BIV
- Problem dialectially improper response. Also
does not explain why we think the first premise
is intuitive.
27Deny second premise
- 2. K BIV ? -K hands
- Underlying this premise is the closure principle
for knowledge - If you know that p, and if you know that p
implies q, then you know that q. - If you know that you have hands, and if you know
that having hands implies not being a BIV, then
you know that you are not a BIV. - But you dont know that you are not a BIV.
- So you dont know that you have hands.
28Problems
- Closure highly intuitive.
- No explanation of why closure is mistakenly taken
to be so intuitive.
29Idealism?
- The view that knowledge of the external world is
not knowledge independent of our perception of
it, but rather is constituted by our perception. - The external world is a construct out of our
appearances.
30Desideratum
- Must explain why we thought the premise so
intuitive even though it appears false.
31Knowledge and MindThursday April 26th 2007
32Sceptical paradox
- 1. K BIV
- 2. K BIV ? -K hands
- 3. K hands
33Solutions to scepticism
- 1. Mooreanism (deny premise 1)
- 2. Anti-closure (deny premise 2)
- 3. Contextualism
34Anti-closure
- 2. K BIV ? -K hands
- Underlying this premise is the closure principle
for knowledge - If you know that p, and if you know that p
implies q, then you know that q. - If you know that you have hands, and if you know
that having hands implies not being a BIV, then
you know that you are not a BIV. - But you dont know that you are not a BIV.
- So you dont know that you have hands.
35Problems
- Closure highly intuitive.
- No explanation of why closure is mistakenly taken
to be so intuitive.
36Contextualism
- Intuition the word knows means the same thing
in every context of use. - If we deny this intuition, we might have a way
out of the sceptical paradox. - Specifically the word knows means two
different things either it means knows
according to high standards, or it means knows
according to low standards.
37Example Bank Case A
- Suppose that you are driving home with your wife
on a Friday afternoon. You plan to stop at the
bank on the way home to deposit your paychecks.
But driving past the bank, you notice that the
lines inside are very long. Fortunately, in this
case it is not important that the checks be
deposited right away, so you suggest to drive
straight home and deposit the pay checks on
Saturday morning. Your wife says, Maybe the bank
wont be open tomorrow. Lots of banks are closed
on Saturdays. You reply, No, I know itll be
open. I was just there two weeks ago on Saturday.
Its open until noon.
38Example Bank Case B
- Now suppose that everything is as in the previous
case, besides this youve just written a very
large and very important check, which will bounce
when not deposited into your checking account
before Monday morning.And, of course, the bank is
not open on Sunday.Your wife reminds you of these
facts. She then says, Banks do change their
hours. Do you know the bank will be open
tomorrow? - Remaining as confident as you were before that
the bank will be open then,still,you
reply,Well,no.Id better go in and make sure.
39Intuitions
- Bank case A knowledge
- Bank case B no knowledge
- Conclusion knows must mean different things in
different contexts.
40Contextualism
- The truth-conditions of knowledge sentences
fluctuate with changes in the context. - So skp might be true in a low-standards
context, but might be false in a high-standards
context.
41Versions of contextualism
- 1. Standards for knowledge fluctuate.
- 2. The amount of alternatives you have to
eliminate fluctuates.
42Contextualism and scepticism
- No knowledge in high-standards contexts.
- Knowledge in low-standard contexts.
- So long as sceptical scenarios are not
mentioned, we know propositions about the
external world.
43Alternative explanation for bank cases
- Warranted assertability maneuver 1
- Bank Case A there is knowledge
- Bank Case B there is knowledge, but it would be
unwarranted to assert that there is knowledge in
this case. - We have confused the truth of the knowledge
sentence with its assertability conditions.
44- Warranted Assertability maneuver 2
- There is no knowledge in Bank Case A, but it is
warranted to assert that there is - There is no knowledge in Bank Case B
- We have confused the truth value with the
conditions for warranted assertion.
45Tuesday, May 1stKnowledge and Mind
- Contextualism and Scepticism
- Sceptical Paradox
- Three solutions to the paradox
- New solution contextualism
- Problem with contextualism
46Practical information
- Exam answer three questions out of 8.
- There will be no division in the exam paper
between mind and knowledge. You can do - 3 mind, 0 knowledge
- 0 mind, 3 knowledge
- 2 mind, 1 knowledge
- 1 mind, 2 knowledge
47Sceptical Paradox
- 1. K BIV
- 2. K BIV ? -K hands
- 3. K hands
48Solutions to the sceptical paradox
- 1. Mooreanism (deny premise 1)
- 2. Anti-closure (deny premise 2)
- 3. Scepticism (accept)
- Always explain why the claim you deny or accept
seemed intuitive but actually is false.
49Problems with these solutions
- All are counterintuitive.
- New solution contextualism. Defended by Keith
DeRose, Stewart Cohen, David Lewis.
50Contextualism
- Intuition the word knows means the same thing
in every context of use. - If we deny this intuition, we might have a way
out of the sceptical paradox. - Specifically the word knows means two
different things either it means knows
according to high standards, or it means knows
according to low standards.
51Motivating contextualism The Bank Cases.
- Bank Case A Suppose that you are driving home
with your wife on a Friday afternoon. You plan to
stop at the bank on the way home to deposit your
paychecks. But driving past the bank, you notice
that the lines inside are very long. Fortunately,
in this case it is not important that the checks
be deposited right away, so you suggest to drive
straight home and deposit the pay checks on
Saturday morning. Your wife says, Maybe the bank
wont be open tomorrow. Lots of banks are closed
on Saturdays. You reply, No, I know itll be
open. I was just there two weeks ago on Saturday.
Its open until noon.
52Motivating contextualism The Bank Cases.
- Bank Case B Now suppose that everything is as in
the previous case, besides this youve just
written a very large and very important check,
which will bounce when not deposited into your
checking account before Monday morning. And, of
course, the bank is not open on Sunday. Your wife
reminds you of these facts. She then says, Banks
do change their hours. Do you know the bank will
be open tomorrow? - Remaining as confident as you were before that
the bank will be open then, still, you reply,
Well, no. Id better go in and make sure.
53Intuitions
- Bank case A knowledge
- Bank case B no knowledge
- Conclusion knows must mean different things in
different contexts.
54Contextualism
- The truth-conditions of knowledge sentences
fluctuate with changes in the context. - So skp might be true in a low-standards
context, but might be false in a high-standards
context.
55Contextualism and scepticism
- No knowledge in high-standards contexts.
- Knowledge in low-standard contexts.
- So long as sceptical scenarios are not
mentioned, we know propositions about the
external world.
56Contextualism and Scepticism
- Both the sceptic and the non-sceptic are correct.
- 1. K BIV true in a sceptical context, but
false in a non-sceptical context. - 2. K BIV ? -K hands
- 3. K hands true in a sceptical context, but
false in a non-sceptical context
57Problem for contextualism
- Warranted assertability maneuver 1
- Bank Case A there is knowledge
- Bank Case B there is knowledge, but it would be
unwarranted to assert that there is knowledge in
this case. - We have confused the truth of the knowledge
sentence with its assertability conditions.
58Problem for contextualism
- Warranted Assertability maneuver 2
- There is no knowledge in Bank Case A, but it is
warranted to assert that there is - There is no knowledge in Bank Case B
- We have confused the truth value with the
conditions for warranted assertion.