Conditional Proofs

[Dillinger4]

Not really a math question but has anyone had any experience working with proofs? I need to present a proof to my intermediate logic class and i want to know if it's correct or not.

[twanvl]

There are many kinds of proofs. If it's not a 50 page monstrosity you can post it here. It never hurts to try.

[DiGiTaIErRoR]

If all else fails...

try...

"YOU KNOW DAMN WELL!"

[Acidic]

a mathematical proof?
or deductive knowledge, and thereby proof?

Then we could branch off and talk about religious proof?

Or how different cultures have different proofs.

I reckon (hmm. I very rarely use that word) that deductive knowledge is by far the easiest to explain and defend.

bob got below 55% in his maths exam
averyone below 55% fails, therefore Bob fails. The problem is, the more specific you are, the easier it is to be proven wrong.

[DiGiTaIErRoR]

That's why it's conditional...

Like... if a=b and b=c then a=c.

[Dillinger4]

Posted by DiGiTaIErRoR

That's why it's conditional...

Like... if a=b and b=c then a=c.

Yes exactly. A basic proof in prepositional logic would look somthing like this. 1.) if a then b
2.) ~b / ~a

So you would have to figure out how to derive ~a using rules of inference. So the completed proof would look like this.

1.) if a then b
2.) ~b / ~a
3). ~a modus ponens 1,2

Natural deduction is equal to the power of a truth table as far as proving validity but it cannot be used with any facility to prove invalidity.