That was a conclusion from the theory of Relativity.

I thought that if someone knew that a proposition was false, then necessarily he would know that it was true that the proposition was false. So you cannot know only that propositions are false, since to do that you have to know that the proposition that they are false is, itself, true.

So you don't believe that humans can know anything?

We know what we make. We don't make the universe. We make systems of logic. We know 1 + 1 = 2.

Luckily we don't have to get bogged down in theoretical physics to settle this because your claim is false on the face of it. No theory in general can support a distinction that's untestable. The difference between whether or not something can't happen or doesn't happen is not testable. In either case it doesn't happen.

Who said we make the universe?

Just because we don't make the universe doesn't mean we can't know facts about the universe. Why would you think that?

No one. And I never implied or claimed otherwise.



The reason why claims about the universe are a matter of doubt is the same reason why 1 + 1 = 2 isn't a matter of doubt.

There is no distinction between the proposition that a person does not jump 100 feet into the air, and the proposition that he cannot jump 100 feet into the air?

If someone asked you, why don't you fly like the birds rather than walking, is your answer simply, "Because I don't?" (And not, because I can't, since I have no wings)?

No one. And I never implied or claimed otherwise.

The reason why claims about the universe are a matter of doubt is the same reason why 1 + 1 = 2 isn't a matter of doubt.

When you state things to people, people usually assume there is a reason why you stated them.

This is the problem you and I ran into earlier when you said you aren't seeking what is obviously false. Why you tell me these things, but have no reason, I do not know.



Please explain.

Are you telling me that when I try and fail to do something physically impossible, I'm supposed to feel something different than when I try and fail to do something physically possible?

Well, I don't. They both feel the same. They both result in the same observations and predictions. In fact, the difference isn't testable at all.



When I go out in the backyard and flap my arms, I don't feel that I have tried to do the impossible. I just feel that I have tried to do something and failed. Sometimes I try to do things and fail but I don't therefore assert that they are impossible.

I never heard anyone say that the difference between what is impossible, and what is possible, but isn't done, is a matter of feeling? I might feel I can leap 100 feet in into the air, but that does not mean it is physically possible for me to do such a thing. What difference does what one feels have to do with it?

Are you seriously telling me that you don't know that not only do you now fly, even when you try (have you tried?) but that you cannot fly.

How about running the one minute mile? You don't do it, but can you run a mile in one minute? What if you were offered a millon dollars to run the one minute mile. Would you take a shot at it?

Of course the test of whether something is impossible is not to try and fail to do it. Who said it was. Do you think that the way do decide whether you can run a one minute mile is to try to do it and fail? And that, even then, that isn't really a test?

Of course the test of whether something is impossible is not to try and fail to do it.

Besides a priori knowledge (instincts) trial and error is the only method to assert what is possible to achieve...reason itself is build-up in this way, down the Historical Process...

---------- Post added 03-04-2010 at 12:08 PM ----------

Ask a 6 year old child who perfectly knows what running, a mile, and a minute is, if he can do a one minute mile... and probably you will get surprised with the answer he will give you.

What is it then? Explain how you know something is physically impossible. If it's not by intuition, observation or experiment then what else is left?

I know it is impossible to come back from the dead, but not by trying and failing.

How then? You haven't yet offered a cogent explanation of how you come to determine something is physically impossible.

For instance, it follows from relativity theory that no velocity can exceed the velocity of light.

Please show us exactly how it follows without invoking the fallacies of "I've never observed x therefore x is physically impossible" or "I've never failed to observe x therefore x is physically necessary".

Of course you can't do it because all theories are based on observations and you can never observe that something can't happen rather than simply doesn't happen.

I really do not know enough Relativity theory to undertake such a task