Two directions in presenting arguments

I sometimes get on other discussion boards to learn about new things. On one I regularly frequent, there was a new person who came on saying, "Prove God exists." The way this person was arguing his/her point had plenty of flaws in it, but anyway. Still, it got me thinking of 2 different ways to make a case/argument for something. There is a difference between presenting a positive case for something, and a negative case against something.

A Positive Case
This is where you basically give evidence (and it doesn't have to always come from science!) for believing something is true. It's where we present "premises"... things that we agree on, the evidence, etc., then we show why these premises lead to a certain conclusion.

Here's an example: I heard a pop, followed by a sound of something fizzing, then I heard someone drinking something. I came into the room and saw Kyle holding an opened Sprite can. Conclusion: Kyle just drank some Sprite while I was in the other room. (Is it possible that it was someone else that drank something and it just so happened to be that Kyle was holding a Sprite can? Yes. But based on the evidence presented, I have good reason to believe that it was Kyle who made the drinking sounds even though I didn't see it.)

A Negative Case
Many atheists will argue a negative case against theism (those who believe there is a god or gods... theists include not only Christians, but also Muslims, polytheists, Jews, Hindus, etc.). Many atheists think that if there is NO good argument for a god existing, they then think that they've proven that atheism is true. They want theists to give reasons for a god's existence, and then in one way or another, they dismiss all of those reasons.

However, what they've done is this: they haven't proven atheism... they've only dismissed the arguments for theism. They haven't shown that theism itself isn't true; they've only weakened the theist's case for a god existing. But this does not strengthen their case for atheism. Huuuuuuge difference!

Here's an example: Heather (Lynch, of course... not me!) says cats can fly on their own without anyone throwing them. Nobody has seen a cat fly on its own. Therefore flying cats don't exist. (Has this proven that flying cats don't exist??? No. It only proves that I haven't seen one.)

So negative cases don't prove anything... they only disprove. Positive cases don't disprove, they only aim to prove.