An Epistemic logic..

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kennethamy
 
Reply Wed 26 May, 2010 03:58 pm
@ughaibu,
ughaibu;169232 wrote:
Are you serious, have you actually done this? If your example was believing a person to be both stupid and intelligent, I would accept it, but the example you gave. . . .


Have never confused appointments? Have you never believed both that you had a dentist's appointment and (say) a physician's appointment at the very same time, and realized that you believed you had to be in two places at the same time.
 
ughaibu
 
Reply Wed 26 May, 2010 04:13 pm
@kennethamy,
kennethamy;169238 wrote:
Have never confused appointments? Have you never believed both that you had a dentist's appointment and (say) a physician's appointment at the very same time, and realized that you believed you had to be in two places at the same time.
These examples too, are quite different from believing both that water has the chemical composition H2O and water doesn't have the chemical composition H2O, aren't they? However, I assume that you have here stated that you have held directly contradictory beliefs.
 
kennethamy
 
Reply Wed 26 May, 2010 04:55 pm
@ughaibu,
ughaibu;169240 wrote:
These examples too, are quite different from believing both that water has the chemical composition H2O and water doesn't have the chemical composition H2O, aren't they? However, I assume that you have here stated that you have held directly contradictory beliefs.


I have, anyway, and I would be surprised if you hadn't. It is not psychologically impossible so far as I can see. And from the fact that two statements contradict one another, it does not follow that you cannot believe both of them.
 
ughaibu
 
Reply Wed 26 May, 2010 05:10 pm
@kennethamy,
kennethamy;169254 wrote:
from the fact that two statements contradict one another, it does not follow that you cannot believe both of them.
But your example seems to me to be trivial. I have, of course, actual experience of over-booking myself, that is to say that I have been actually committed to being in two different places at the same time, so my belief that I should be in two different places at the same time was correct. If you think that there is a contradiction in this, then there are true contradictions and these true contradictions can be known. But I doubt very much that you believe that there are true contradictions, so I doubt very much that you believe that you've provided a contradiction with your example. Or do you believe that you have offered an example which is both a contradiction and not a contradiction?
 
kennethamy
 
Reply Wed 26 May, 2010 05:20 pm
@ughaibu,
ughaibu;169260 wrote:
But your example seems to me to be trivial. I have, of course, actual experience of over-booking myself, that is to say that I have been actually committed to being in two different places at the same time, so my belief that I should be in two different places at the same time was correct. If you think that there is a contradiction in this, then there are true contradictions and these true contradictions can be known. But I doubt very much that you believe that there are true contradictions, so I doubt very much that you believe that you've provided a contradiction with your example. Or do you believe that you have offered an example which is both a contradiction and not a contradiction?


That doesn't show there are true contradictions. It shows that a person may believe two propositions which contradict each other. Are you asserting that this is psychologically impossible? On what evidence?
 
ughaibu
 
Reply Wed 26 May, 2010 05:25 pm
@kennethamy,
kennethamy;169263 wrote:
That doesn't show there are true contradictions. It shows that a person may believe two propositions which contradict each other.
The propositions, in your example, dont contradict each other. Returning to Zetherin's example, that he can believe both that the chemical composition of water is and is not H2O, you claim to have held directly contradictory beliefs, such as this. What is your example?
 
kennethamy
 
Reply Wed 26 May, 2010 05:46 pm
@ughaibu,
ughaibu;169264 wrote:
The propositions, in your example, dont contradict each other. Returning to Zetherin's example, that he can believe both that the chemical composition of water is and is not H2O, you claim to have held directly contradictory beliefs, such as this. What is your example?


That my girlfriend is faithful and that she is not faithful. How is that? Medievals might have given the example that God is a being greater than which cannot be conceived, and that God does not exist. Some ancient mathematicians believed that a figure which was a circle could also be squared. What difference does the example make? Could not an insane person hold contradictory beliefs? I really don't see the problem. Imagine someone holding that someone was his male parent but not believing that someone was his father. He simply did not realize that all male parents are fathers. Why is that impossible?
 
ughaibu
 
Reply Wed 26 May, 2010 05:51 pm
@kennethamy,
kennethamy;169275 wrote:
That my girlfriend is faithful and that she is not faithful. How is that?
Redundant, as I already gave the example of believing that a person is both stupid and intelligent.
kennethamy;169275 wrote:
What difference does the example make?
Do you think it's true that there is a person, Zetherin or other, who believes both that the chemical composition of water is and is not H2O?
 
kennethamy
 
Reply Wed 26 May, 2010 05:57 pm
@ughaibu,
ughaibu;169277 wrote:
Redundant, as I already gave the example of believing that a person is both stupid and intelligent. Do you think it's true that there is a person, Zetherin or other, who believes both that the chemical composition of water is and is not H2O?


Absolutely no idea. How would I know what some people believe? I don't, Zeth. doesn't. A person might very well believe that water is H2O and also believe some proposition that entails that water is not H2O. Any reason why not?
 
ughaibu
 
Reply Wed 26 May, 2010 06:02 pm
@kennethamy,
kennethamy;169283 wrote:
Absolutely no idea. How would I know what some people believe?
Then your response to post 20, and the subsequent ten posts appear to be idle chit-chat of no relevance to the thread. Thanks for that.
 
Zetherin
 
Reply Wed 26 May, 2010 06:23 pm
@Owen phil,
ughaibu wrote:
Do you think it's true that there is a person, Zetherin or other, who believes both that the chemical composition of water is and is not H2O?


Suppose the answer is no. So what? Does that mean that it's psychologically impossible for someone to believe that particular set of contradictory propositions?

What exactly is the point you're making? Simply that that particular set of contradictory beliefs is less likely to be held by someone than other sets? Sure, maybe that is true, but what does that change about my initial point?
 
ughaibu
 
Reply Wed 26 May, 2010 06:28 pm
@Zetherin,
Zetherin;169293 wrote:
What exactly is the point you're making?
That examples should be at least plausible. The implications of plausible examples are likely to be quite different from those of dramatic pseudo-examples, such as the one that you offered. Sloppiness in presentation wastes everyone's time, (except perhaps Kennethamy's).
 
Zetherin
 
Reply Wed 26 May, 2010 06:29 pm
@ughaibu,
ughaibu;169299 wrote:
That examples should be at least plausible. The implications of plausible examples are likely to be quite different from those of dramatic pseudo-examples, such as the one that you offered. Sloppiness in presentation wastes everyone's time, (except perhaps Kennethamy's).


And what makes you think my example isn't plausible?
 
ughaibu
 
Reply Wed 26 May, 2010 06:31 pm
@Zetherin,
Zetherin;169300 wrote:
And what makes you think my example isn't plausible?
You land on a snake, go back to post 20.
 
Zetherin
 
Reply Wed 26 May, 2010 06:35 pm
@ughaibu,
ughaibu;169301 wrote:
You land on a snake, go back to post 20.


This is post #20:

ughaibu wrote:
Are you serious, have you actually done this? If your example was believing a person to be both stupid and intelligent, I would accept it, but the example you gave. . . .


Yeah, that post describes in great detail why my example is implausible.

*eats your damn snake*
 
ughaibu
 
Reply Wed 26 May, 2010 06:40 pm
@Zetherin,
Zetherin;169303 wrote:
that post describes in great detail why my example is implausible.
Have you ever held a pair of directly contradictory beliefs that are equivalent to the pair:
1) the chemical composition of water is H2O
2) the chemical composition of water is not H2O?
If not, then your example enjoys no plausibility. Personally, I have never held such a pair of beliefs, so your example is, on the face of it, implausible.
 
Zetherin
 
Reply Wed 26 May, 2010 06:44 pm
@Owen phil,
ughaibu wrote:
If not, then your example enjoys no plausibility. Personally, I have never held such a pair of beliefs, so your example is, on the face of it, implausible.


That I haven't held that pair of contradictory beliefs, means that it is implausible for someone to hold that pair of contradictory beliefs?

I've also never been in a plane crash. I suppose plane crashes are implausible too, right?
 
ughaibu
 
Reply Wed 26 May, 2010 06:48 pm
@Zetherin,
Zetherin;169311 wrote:
That I haven't held that pair of contradictory beliefs. . . .
In short, and as I said, your example is implausible.
Zetherin;169229 wrote:
I can believe that the chemical composition of water is H2O, and I can believe that the chemical composition of water is not H2O.
I've had enough of wasting my time on this, I suggest that if you had a point for Owen, then you find a suitable example and resubmit whatever it was you were getting at in post 19.
 
Zetherin
 
Reply Wed 26 May, 2010 06:58 pm
@Owen phil,
ughaibu wrote:
In short, and as I said, your example is implausible.


I'm wholly aware you think that. But why you think that, I still haven't a clue.
 
Owen phil
 
Reply Wed 26 May, 2010 08:56 pm
@Zetherin,
Zetherin;169229 wrote:
I think your error is that you believe that for contradictory beliefs to be held, that there must be a contradictory happening (p and ~p). But this isn't true.

For instance, I can believe that the chemical composition of water is H2O, and I can believe that the chemical composition of water is not H2O. But that I believe both, as we know, doesn't mean both propositions are true. We know that one is false.

Contradictory happenings are believable, but that doesn't imply that there are contradictory happenings. What we believe and what is, are two different things.


B(p & ~p) <-> ~K(p v ~p) but, all tautologies are knowable by
1. (p is a tautology) -> Kp.

That is, K(p v ~p) is valid and therefore, ~K(p v ~p) is contradictory.
That is, ~K~(~p & p) is contradictory. Therefore, B(~p & p) is a contradiction.

~B(p & ~p), it is not believable that (p is true and p is false), is a theorem of this logic.
 
 

 
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