Here's something I'd like to run by you guys.  How do we go about proving something?  Let's say there's a theory, like "All birds have wings."  I have no idea if this is true or not, but bear with me.  How do we go about proving this theory?
This may seem a bit asinine, but I'm going somewhere with it.  Let's just start off slowly, though :)

All birds do have wings, just they don't necessarily fly.

Well, generally (if applicable) you would start out with visual observation. Yes?

Okay, great.  So we get empirical evidence to just go out and look at birds, exactly.
So we go out and don't find any birds without wings, what does that prove?

Yeah, I'm not an adult so I won't go very far with this. Not an adult at all...

But I do know that it proves that to classify an animal or being as a bird, the animal must have wings.

Right, but I'm talking about just proving some random idea.  I just picked birds having wings because that was the first thing I thought of.  We could say that all finches are brown (again, I have no idea).  So I go out and study 10,000 birds or finches or whatever and I find that all of them have the characteristic (wings, brownness, whatever) that I am looking for.  What does that prove?

If 10,000 finches are brown and have wings, it proves that all (or almost all) fit those characteristics.

Actually, if 10,000 finches are brown and have wings it does not prove that all of them fit those characteristics, it just shows that 10,000 finches have those characteristics.

And so here we run into our first dilemma.  10,000 finches is a lot of finches... a LOT.  But can we really say that it proves anything more than the statement "At least 10,000 finches are brown."  -  or whatever it is we're studying now.

Alright, that makes sense.  So where is this going Moegreche?  Honestly I have no idea where you are going haha.

Okay, here's the point:

In order to prove an theory, we'd have to observe every possible instance of the theory, and anything that falls outside of the theory disproves it, right?
Well, let's say my theory is that "All alligators are under 50 feet" and then I find an alligator that is 49 feet and 11.5 inches.  Technically, that doesn't disprove my theory, but I am now really concerned that this sure thing might be out the window!  So instances of a theory can actually disprove a theory it seems.
Here's another example with the brown finch thing.  In order to prove my theory I'm going to go look at blue bottle tops.  Now, why on earth would I go look at blue bottle tops to prove that all finches are brown?
Whoops, have to run really quickly.  What do you guys think about the first part?  Does a 49 foot 11.5 inch alligator disprove my theory?  This goes into what is proof.  Do I really have to look at all alligators to prove my scientific theory?
If anyone can figure out why I need to look at blue bottle tops to prove that all finches are brown, I'll buy you an ice cream cone!  Seriously, we'll figure out a way for me to get an ice cream cone to you.