I know that I know

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Zetherin
 
Reply Tue 9 Feb, 2010 11:45 pm
@ACB,
ACB;126606 wrote:
Yes. The problem is that one cannot consistently claim both (i) "I know A", "I know B", "I know C" etc, and (ii) "I do not know the conjunction of A+B+C etc". And since it would be unreasonable to deny (ii), the difficulty lies with (i).


What is the conjunction of A+B+C? What would the actual claim in (ii) be? "I don't know anything"? Who would claim, "I don't know anything", after claiming they know something?
 
kennethamy
 
Reply Wed 10 Feb, 2010 12:30 am
@ACB,
ACB;126606 wrote:
Yes. The problem is that one cannot consistently claim both (i) "I know A", "I know B", "I know C" etc, and (ii) "I do not know the conjunction of A+B+C etc". And since it would be unreasonable to deny (ii), the difficulty lies with (i).

---------- Post added 02-10-2010 at 03:12 AM ----------



.


It is not unreasonable to deny (ii). What is unreasonable is to deny the conjunction of (i) and (ii).
 
fast
 
Reply Wed 10 Feb, 2010 08:15 am
@Emil,
[QUOTE=Emil;126589]I think you are wrong. Here is why.

Yes, it is not a contradiction, but a contradiction (P and not-P) can be deduced from it. That is what is relevant after all.

[/QUOTE]Then I'm not wrong am I? I say it's not a contradiction, it's not a contradiction, and you agree that it's not a contradiction. That a contradiction can be reduced from it (as you say) may be important; in fact, it may be very important, but it has no bearing (so far as I can tell) on whether I'm right or wrong.

I do appreciate your post, however. I saw then (and continue to see now) that there is a problem when "may" is used, but I didn't know that the problem I saw ought to be characterized as something that implies a contradiction. Had I realized how to characterize it, I probably should have mentioned it when denying (and rightly so) that there is no contradiction.
 
kennethamy
 
Reply Wed 10 Feb, 2010 08:26 am
@fast,
fast;126726 wrote:
Then I'm not wrong am I? I say it's not a contradiction, it's not a contradiction, and you agree that it's not a contradiction. That a contradiction can be reduced from it (as you say) may be important; in fact, it may be very important, but it has no bearing (so far as I can tell) on whether I'm right or wrong.

I do appreciate your post, however. I saw then (and continue to see now) that there is a problem when "may" is used, but I didn't know that the problem I saw ought to be characterized as something that implies a contradiction. Had I realized how to characterize it, I probably should have mentioned it when denying (and rightly so) that there is no contradiction.


If a contradiction can be inferred from a statement, then that statement is a contradiction.
 
ACB
 
Reply Wed 10 Feb, 2010 09:05 am
@Zetherin,
Zetherin;126620 wrote:
What is the conjunction of A+B+C? What would the actual claim in (ii) be? "I don't know anything"? Who would claim, "I don't know anything", after claiming they know something?


No, the claim in (ii) would be "I don't know collectively everything that I claim to know individually" or "I don't know collectively everything that I confidently believe individually".

It is reasonable to claim to know collectively most of what one claims to know individually. If one has strong justification for believing a large number of things, it is likely that most of them are true, but that a few are not. One would have to be extraordinarily lucky to go through life without having any of one's confident beliefs proved wrong.
 
kennethamy
 
Reply Wed 10 Feb, 2010 09:16 am
@ACB,
ACB;126731 wrote:
No, the claim in (ii) would be "I don't know collectively everything that I claim to know individually" or "I don't know collectively everything that I confidently believe individually".

It is reasonable to claim to know collectively most of what one claims to know individually. If one has strong justification for believing a large number of things, it is likely that most of them are true, but that a few are not. One would have to be extraordinarily lucky to go through life without having any of one's confident beliefs proved wrong.


Why did you switch from knowing to believing? What you say is, of course, true of believing, but not true of knowing.
 
fast
 
Reply Wed 10 Feb, 2010 09:18 am
@kennethamy,
[QUOTE=kennethamy;126727]If a contradiction can be inferred from a statement, then that statement is a contradiction.[/QUOTE]
Fine. A contrary can be inferred from the statement, not a contradiction, so the statement is not a contradiction.

I do better at seeing contradictions (contradictory statements) when I'm comparing two statements, so I'll break the sentence apart. The sentence is, "I know that P, but for all I know, P may be false." I'll break it down into the following statements:

P1-1: I know that P.
P2-1: P may be false.

Knowledge implies truth, so P1-1 implies that P is true. Here it is written out:

P1-1: I know that P.
P1-2 (an implication of P1-1): P is true.
P2-1: P may be false

We cannot imply that P is true from P2-1, so we cannot conclude that P is true based on P2-1.

Moving on:
A statement doesn't exist in a vacuum, so I'll assume that the statements are being asserted. We would not assert P1-1 unless we believed we had a good reason to believe P is true, so it's inconsistent for someone to assert P1-1 (that has the implication that they have a good reason to believe P is true) and assert P2-1 (that has the implication that they have a good reason to believe P is false), but since when is that a contradiction?
 
ACB
 
Reply Wed 10 Feb, 2010 09:32 am
@kennethamy,
kennethamy;126634 wrote:
It is not unreasonable to deny (ii).


To deny (ii) is to claim that none of your vast number of confident beliefs is wrong. (That is to say, it is logically possible for them to be wrong, but in fact none are.) But do you seriously believe this? Have you never experienced astonishment, arising from the falsification of something you were utterly convinced was true? And do you not expect to experience it again at some time?

kennethamy;126634 wrote:
What is unreasonable is to deny the conjunction of (i) and (ii).


I think you mean: "What is unreasonable is to claim the conjunction of (i) and (ii)". (Look at my wordings again.) And I would agree with that.
 
kennethamy
 
Reply Wed 10 Feb, 2010 09:32 am
@fast,
fast;126733 wrote:

Fine. A contrary can be inferred from the statement, not a contradiction, so the statement is not a contradiction.

I do better at seeing contradictions (contradictory statements) when I'm comparing two statements, so I'll break the sentence apart. The sentence is, "I know that P, but for all I know, P may be false." I'll break it down into the following statements:

P1-1: I know that P.
P2-1: P may be false.

Knowledge implies truth, so P1-1 implies that P is true. Here it is written out:

P1-1: I know that P.
P1-2 (an implication of P1-1): P is true.
P2-1: P may be false

We cannot imply that P is true from P2-1, so we cannot conclude that P is true based on P2-1.

Moving on:
A statement doesn't exist in a vacuum, so I'll assume that the statements are being asserted. We would not assert P1-1 unless we believed we had a good reason to believe P is true, so it's inconsistent for someone to assert P1-1 (that has the implication that they have a good reason to believe P is true) and assert P2-1 (that has the implication that they have a good reason to believe P is false), but since when is that a contradiction?


A contrary to what? I am just pointing out that what implies a contradiction is, itself, a contradiction. I don't understand what you mean when you say a contrary can be inferred from a statement.

---------- Post added 02-10-2010 at 10:42 AM ----------

ACB;126734 wrote:
To deny (ii) is to claim that none of your vast number of confident beliefs is wrong. (That is to say, it is logically possible for them to be wrong, but in fact none are.) But do you seriously believe this? Have you never experienced astonishment, arising from the falsification of something you were utterly convinced was true? And do you not expect to experience it again at some time?



I think you mean: "What is unreasonable is to claim the conjunction of (i) and (ii)". (Look at my wordings again.) And I would agree with that.



But, (ii) implies the negation of i. So it is unreasonable to assert (not deny, of course) the conjunction of (i) and (ii).
 
Emil
 
Reply Wed 10 Feb, 2010 10:06 am
@fast,
fast;126726 wrote:
Then I'm not wrong am I? I say it's not a contradiction, it's not a contradiction, and you agree that it's not a contradiction. That a contradiction can be reduced from it (as you say) may be important; in fact, it may be very important, but it has no bearing (so far as I can tell) on whether I'm right or wrong.

I do appreciate your post, however. I saw then (and continue to see now) that there is a problem when "may" is used, but I didn't know that the problem I saw ought to be characterized as something that implies a contradiction. Had I realized how to characterize it, I probably should have mentioned it when denying (and rightly so) that there is no contradiction.


Then you are/were only wrong in spirit. What is important is whether a contradiction can be deduced from it, not whether it is a contradiction. Some people do, however, use the term "contradiction" for both what I mean by contradiction (a proposition of the form P and not-P) and any proposition from which a contradiction (in my sense) can be deduced. See Ken's post.

---------- Post added 02-10-2010 at 05:12 PM ----------

ACB;126606 wrote:
Yes. The problem is that one cannot consistently claim both (i) "I know A", "I know B", "I know C" etc, and (ii) "I do not know the conjunction of A+B+C etc". And since it would be unreasonable to deny (ii), the difficulty lies with (i).


Careful with this formulation. What exactly is meant by the conjunction of A+C+B? (I suppose you may mean A∧B∧C?). There is a difference between knowing that A and knowing that B and knowing that C etc. and knowing that (A∧B∧C). Even though A∧B∧C is deducible from A and B and C, it does not logically follow that one knows the conjunction.

Even what I wrote above is not terribly clear but it so hard to talk about this particular distinction because of the way english works.

My point is that if by (ii) you meant the conjunction of knowledges of A, B, C etc., then I agree that it is inconsistent. But it is not, I think, inconsistent to know that A and know that B and know that C etc. and not know the conjunction A∧B∧C etc.
 
fast
 
Reply Wed 10 Feb, 2010 10:18 am
@kennethamy,
[QUOTE=kennethamy;126735]A contrary to what? I am just pointing out that what implies a contradiction is, itself, a contradiction. I don't understand what you mean when you say a contrary can be inferred from a statement.[/QUOTE]Yes, I understand what you pointed out. Thank you. And fine, I'll accept that. But, we still shouldn't call a statement that doesn't imply a contradiction a contradiction.

The complex statement, "I am in Florida, and I am not in Florida" is a contradictory statement, for the simple statements "I am in Florida" and "I am not in Florida" contradict one another.

The complex statement, "I am in Florida, and I am in South Carolina" is a contrary statement, for the simple statements "I am in Florida" and "I am in South Carolina" are contrary to each other.

The complex statement, "I know that P, but for all I know, P may be false" can be broken apart into simple statements just as I did in the previous two examples: "I know P" and "P may be false."

You said that what implies a contradiction is, itself, a contradiction, so let's see what "I know P" implies to see if it (along with "P may be false") implies a contradiction, for if it does, then the complex statement is, itself, a contradiction.

Knowledge implies truth, so "I know P" implies P is true, but the simple statement "P is true" (an implication of "I know P") and the simple statement, "P may be false" are not contradictory statements, so we have yet to derive the conclusion that the complex sentence is contradictory.

You, I, nor anyone else should say that we know P unless we have a good reason to think P is true, but be that as it may, it's still not the case that "P may be true" and "P may be false" are contradictory statements, so although the complex statement may not be contradictory, it is contrary-in other words, some implications of the simple sentences derived from the complex statement are contrary to one another.
 
Emil
 
Reply Wed 10 Feb, 2010 10:18 am
@fast,
fast;126733 wrote:

Fine. A contrary can be inferred from the statement, not a contradiction, so the statement is not a contradiction.

I do better at seeing contradictions (contradictory statements) when I'm comparing two statements, so I'll break the sentence apart. The sentence is, "I know that P, but for all I know, P may be false." I'll break it down into the following statements:

P1-1: I know that P.
P2-1: P may be false.

Knowledge implies truth, so P1-1 implies that P is true. Here it is written out:

P1-1: I know that P.
P1-2 (an implication of P1-1): P is true.
P2-1: P may be false

We cannot imply that P is true from P2-1, so we cannot conclude that P is true based on P2-1.

Moving on:
A statement doesn't exist in a vacuum, so I'll assume that the statements are being asserted. We would not assert P1-1 unless we believed we had a good reason to believe P is true, so it's inconsistent for someone to assert P1-1 (that has the implication that they have a good reason to believe P is true) and assert P2-1 (that has the implication that they have a good reason to believe P is false), but since when is that a contradiction?


What is a contrary? Contrariness is usually defined in logic discourses as a relation that holds between two propositions iff 1) it is impossible for both to be true, and 2) they can both be false. I'm guessing a contrary would mean a conjunction of two propositions that are contraries.

To say that a person asserts something inconsistent means that the person asserts something or somethings from which a contradiction can be deduced. In Ken's terminology, this is a contradiction. See my earlier post.
 
fast
 
Reply Wed 10 Feb, 2010 10:22 am
@Emil,
[QUOTE=Emil;126743]Then you are/were only wrong in spirit. What is important is whether a contradiction can be deduced from it, not whether it is a contradiction. Some people do, however, use the term "contradiction" for both what I mean by contradiction (a proposition of the form P and not-P) and any proposition from which a contradiction (in my sense) can be deduced. See Ken's post.[/QUOTE]
I'm willing to concede and accept that a statement that implies a contradiction is a contradiction. The issue is now whether or not it's a contradiction-be it through implication or otherwise. See my previous post.
 
Emil
 
Reply Wed 10 Feb, 2010 10:36 am
@fast,
fast;126749 wrote:
Yes, I understand what you pointed out. Thank you. And fine, I'll accept that. But, we still shouldn't call a statement that doesn't imply a contradiction a contradiction.


I don't think he is.

Also, what does "statement" mean? Do you mean sentences or propositions or something in between or something else? I will consider it a synonym for "sentence" in this context.

Quote:
The complex statement, "I am in Florida, and I am not in Florida" is a contradictory statement, for the simple statements "I am in Florida" and "I am not in Florida" contradict one another.


It is a contradiction, yes. If you want to call that "contradictory statement", then fine by me.

Quote:
The complex statement, "I am in Florida, and I am in South Carolina" is a contrary statement, for the simple statements "I am in Florida" and "I am in South Carolina" are contrary to each other.


The example is wrong. It is possible to be in both and so they (the simple statements, in your terminology) are not contrary. I could stand with one foot on each side of the border. This approach also works with the above. So, some additional clarity would be needed for this example. I propose to add the word "wholly" in the sentence and "at the same time" at the end of the sentence. That way I can see no problems with the example.

I think this term "a contrary" (i.e. a noun) is a peculiarity to you. I have never seen it before in my readings of logicians' works.

Quote:
The complex statement, "I know that P, but for all I know, P may be false" can be broken apart into simple statements just as I did in the previous two examples: "I know P" and "P may be false."


I disagree that these are the two parts. The phrase "P may be false" and "for all I know, P may be false" do not mean the exact same. The latter clearly expresses epistemic possibility but the former is interpretable as something else.

Quote:
You said that what implies a contradiction is, itself, a contradiction, so let's see what "I know P" implies to see if it (along with "P may be false") implies a contradiction, for if it does, then the complex statement is, itself, a contradiction.

Knowledge implies truth, so "I know P" implies P is true, but the simple statement "P is true" (an implication of "I know P") and the simple statement, "P may be false" are not contradictory statements, so we have yet to derive the conclusion that the complex sentence is contradictory.


This is correct, but it matters not because of what I wrote just above.

Quote:
You, I, nor anyone else should say that we know P unless we have a good reason to think P is true, but be that as it may, it's still not the case that "P may be true" and "P may be false" are contradictory statements, so although the complex statement may not be contradictory, it is contrary-in other words, some implications of the simple sentences derived from the complex statement are contrary to one another.


I do not agree with your ethical evidentialistic (named after Clifford's ethical evidentialism) thesis "You, I, nor anyone else should say that we know P unless we have a good reason to think P is true" but let's put that aside for now. Pyrrho would probably want to defend it and I am skeptical.

Your last paragraph seems confused. Ken's definition of contradiction is this and let's call it the broad definition of contradiction:
[INDENT]A proposition (or sentence or statement etc.) of the form P and not-P, or a proposition (or sentence etc.) from which a proposition (or sentence or statement etc.) of the form P and not-P is deducible.
[/INDENT]The one I use is this, the strict definition:
[INDENT]A proposition (or sentence or statement etc.) of the form P and not-P.

[/INDENT]A contradiction is deducible from "I know that P, but for all I know, P may be false", namely, "I know that P and I do not know that P.".
 
fast
 
Reply Wed 10 Feb, 2010 11:07 am
@Emil,
[QUOTE=Emil;126754]The example is wrong. It is possible to be in both and so they (the simple statements, in your terminology) are not contrary. I could stand with one foot on each side of the border. [/QUOTE]
I want pictures! Very Happy SERIOUSLY!!!

PS: Georgia girls have the most adorable accents!

Funnin' aside, I'll review what I thought I knew about contraries. Thanks for your review of my post. I'll give it some thought.
 
Emil
 
Reply Wed 10 Feb, 2010 12:09 pm
@fast,
fast;126758 wrote:

I want pictures! Very Happy SERIOUSLY!!!

PS: Georgia girls have the most adorable accents!

Funnin' aside, I'll review what I thought I knew about contraries. Thanks for your review of my post. I'll give it some thought.


I assumed that the states were next to each other. Perhaps they are not. I didn't think of it. If they are not next to each other then you can't be in both at the same time of course. (Cannot as in physically cannot. I'm not sure it is logically impossible.)
 
fast
 
Reply Wed 10 Feb, 2010 12:43 pm
@Emil,
[QUOTE=Emil;126774]I assumed that the states were next to each other. Perhaps they are not. I didn't think of it. If they are not next to each other then you can't be in both at the same time of course. (Cannot as in physically cannot. I'm not sure it is logically impossible.)[/QUOTE]
Exactly. It's not logically impossible; It's not a contradiction.

If I say to another that "I'm in Florida, and oh by the way, I'm also in South Carolina," a person that confuses "contrary" with "contradiction" might say that I have said something contradictory, but the sentence, "I am in Florida" and the sentence "I am in South Carolina" are not contradictory sentences, but the each sentence is contrary to the other.

---------- Post added 02-10-2010 at 01:49 PM ----------

Emil;126754 wrote:
A contradiction is deducible from "I know that P, but for all I know, P may be false", namely, "I know that P and I do not know that P.".

Crap. I missed that.
 
Emil
 
Reply Wed 10 Feb, 2010 01:59 pm
@fast,
fast;126783 wrote:

Exactly. It's not logically impossible; It's not a contradiction.

If I say to another that "I'm in Florida, and oh by the way, I'm also in South Carolina," a person that confuses "contrary" with "contradiction" might say that I have said something contradictory, but the sentence, "I am in Florida" and the sentence "I am in South Carolina" are not contradictory sentences, but the each sentence is contrary to the other.


Alright. But going with Ken's definition "I'm wholly in Florida, and oh by the way, I'm also wholly in South Carolina," is a contradiction. (Unless it is possible that they refer to the same object/space. I don't know.)
 
fast
 
Reply Wed 10 Feb, 2010 09:39 am
@Emil,
edited out by accident.
 
fast
 
Reply Wed 10 Feb, 2010 09:42 am
@fast,
Emil;126805 wrote:
Alright. But going with Ken's definition "I'm wholly in Florida, and oh by the way, I'm also wholly in South Carolina," is a contradiction. (Unless it is possible that they refer to the same object/space. I don't know.)


A: I'm in Florida
B: I'm not in Florida

C: I'm in Florida
D: I'm in South Carolina

A and B (CONTRADICTION): One must be true. One must be false.
C and D (CONTRARY): Neither must be true. Both can be false.

You are saying C and D is a contradiction, but it's not a contradiction, as it's not the case one of the two (C or D) must be true.
 
 

 
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