Consider the following two propositions:
A: There exists extraterrestrial life somewhere in the universe.
B: There does not exist extraterrestrial life anywhere in the universe.
B is just the converse of A. However, B is falsifiable (simply by finding life beyond earth), whereas A is not (because it is impossible to check every location in the universe for life, or to be sure that we haven't missed life in a place we've already checked).
So it would seem that by Popper's falsifiability criterion, B is a scientific statement whereas A is not. But this feels misguided, since both statements are so closely related and don't reference any vague pseudoscience. Both statements feel scientific since they are reasonably precise and could be investigated through empirical methods.
So several questions come to mind:
- Would Popper conclude that B is scientific and A is not?
- Is this a defect in Popper's criterion of falsifiability?
- Have modern philosophers of science refined Popper's ideas in order to better address this problem?