[supercat]

It is testable and therefore is empirical science. For example a human skeleton found in the cambrian would falsify the explaination that humans arose through minor variations over millions of years.

If I claim that the current through a resistor will be proportional to the voltage, not only is it possible that such claim might be disproven if false, it is basically certain. While it is true that many of the claims posed by the historical sciences might turn out to be provably false, there remains the very real possibility that they might be false but in such fashion as can never be proven.

Suppose I hand you a box of cross-cut shredded paper and tell you that it contains half of the shreddings from an accurate copy of the "novel" Gatsby (which is notable for its non-use of the letter "e"). If examination of the shreddings reveals that some of the pieces contain the letter "e", that would constitute proof that the shreddings are not what I claim. If examination of the shreddings reveals that none of the pieces contain the letter "t", that would also disprove my claim. On the other hand, no amount of analysis would be able to prove my claim to be true, and it is possible that my claim could be false and yet no amount of analysis would be able to disprove it.

[bobdsmith]

While it is true that many of the claims posed by the historical sciences might turn out to be provably false, there remains the very real possibility that they might be false but in such fashion as can never be proven.

As is true with all scientific theories and laws, whether within historical sciences or not. Ohms law could be false in a way that could never be shown. Science is a method to try and get as close to the truth as possible, it can't actually get all the way there.

On the other hand, no amount of analysis would be able to prove my claim to be true, and it is possible that my claim could be false and yet no amount of analysis would be able to disprove it.

While you can't ever prove the hypothesis that the book is Gatsby, you have already put it through two tests that could have falsified it (finding an 'e' or a 't'). It passed those tests, and so you can have more confidence in the hypothesis. A rival hypothesis which has not been tested to such a degree is therefore inferior, and a rival hypothesis which cannot be tested should be thrown out right away. That methodology helps to reach the most likely explaination.

Common descent (and through that evolution) has passed many tests that could have falsified it to a level where it is considered beyond doubt. Rival explainations to evolution have either not withstood testing, or avoid testing by being untestable (ie ID) and therefore are not at the same level.