What can science prove?

[Frank]

Of course science (to my knowledge) has never shown (or tried to show) that we really exist (just as no scientist has ever disproven the existence of flying pink gummy bears). However, we can call the fact of our existence an a priori fact, which doesn't require any empirical data beyond reason alone; and thus it may be a presumption underlying any other fact arrived at by conclusive scientific proof or logical argument (assuming the argument structure is sound).

I understand there are weaknesses inherent in inductive reasoning (David Hume made excellent points in this regard three centuries ago). Moreover, I also understand it's popular to say science can't prove anything (because they can't prove the underlying fact of our existence). However, our existence is an a priori fact, and it's fallacious to infer it's a fact that requires proof in order to validate the conclusiveness of any other fact. Same type of tap dance theists seem so fond of (and something like theism can only exist in an environement of intellectual confusion). We do exist, and that's a fact, oh yeah .... a "conclusive" fact.

Our existence is logically provable; I have no doubt of that. That wasn't my point though. You can't go from "we exist" to "science has proven certain things do not exist".

The argument for me existing is based on the argument that the act of asking whether I exist or not is a display of thought; thought being an attribute of something that exists; therefore I exist. Please show me how that can be extended to show other things exist...

In the first instance I simply asserted that it cannot be said science is incapable of conclusively proving anything. Nonetheless, I'll give your challenge a try. Not only are a priori facts defacto conclusive, but so are posteriori facts. Therefore, we can trust that (for example) tunafish exist.

Assuming the fundamental laws of the natural world remain unaltered:

1) All fish now living on earth eventually die
2) Tuna is a type of fish now living on earth
3) Therefore, all tunafish now living on earth will eventually die

It is true that scientists haven't observed every single tuna fish in our oceans. However, the volumes of data they've collected over the centuries with regard to aquatic life makes statements one and two posteriori knowledge. Therefore, through simple deductive reasoning we arrive at the conclusion that all tunafish now living on earth will die (with no exceptions).

This argument is affirmative, however, it also applies in the negative. Here, we can say science has conclusively ruled out the possibility that any tunafish now living on earth can be immortal (and we can say this conclusively). I'm just playing around with the logic here. In truth the fact that all tunafish on earth will eventually die is itself posteriori knowledge (and doesn't require a deductive argument to prove it). By caveat of the same sort of data science can use to prove all fish now living on earth will die, they can prove all tunafish on earth die. Therefore, the same applies in the negative (e.g. they can rule out the possibility of an immortal tunafish; and that conclusion is posteriori knowledge based on scientific data).