Theophage

Nonsense. What of empirical observation and other a posteriori knowledge? Is there some kind of truth other than "Aboslute Truth(tm)"?

Draygomb

Theophage

How do you know what you observed was true?

Theophage

Draygomb,

in order for logic to be on any use, you must proceed from true postulates to a true conclusion.

How do you know any true postualtes?

The answer to both our questions is the same.

Draygomb

Theo

Except Logic doesn't need to rely on observations.

Francois Tremblay

I hope that was said in jest, although I don't see any smileys...

Theophage

Correct, but such logic need not be true either. Consider the following syllogism:

P1) All animals have three legs
P2) Fish are animals
C3) Therefore fish have three legs

Logically, this argument is valid; the conclusion validly follows from the premises even though premise 1 is false. Would you then say that such logic represents "Absolute Truth"? I certainly wouldn't.

Logically valid arguments mean nothing unless they proceed from tru premises, and where do you suppose we get those premises from, eh?

Draygomb

Theo

False + True = False

Logically if your conclusion is false one or more of your premises is false. Just because logic is the only source of absolute truth doesn't mean there is a lot of absolute truthes.

So far I have 4:
1 I exist
2 Math and Logic are reliable
3 God doesn't exist
4 a polygon with x sides can't be a polygon with non-x sides

Draygomb

Franc

What do you need to observe to know that Squares can't be Circles?

Francois Tremblay

I need to already know what a square is, what a circle is, define them, know the laws of logic, all of which involve empirical capacities. From there it's a simple matter of using logic to deduce the proposition you describe.

Draygomb

Franc Empirical means by experience or observation yet the definitions and the rules of logic are enough to prove there are no square circles.