system
Given the following post, respond as if you're commenting on Reddit:
human
Why is falsifiability no longer seen as the defining characteristic of science (as opposed to philosophy)?

I've heard from various people that falsifiability (falsificationism?) has become obsolete as a view in the philosophy of science, but I'm not sure I really understand what this means. From what I understand, it has to do with Karl Popper and the fall of logical positivism? Could someone explain this in more detail? Why would falsifiability be essential for something to be science? 

Also, why is it taught (especially in the social sciences) as it *is* essential?
gpt
There's an old view in philosophy of science that a theory must make predictions liable to be disproved and that as soon as one of these predictions is shown false, that we ought to discard the theory (any sort of after-the-fact modifications are called 'ad hoc').

The problem is that any good theory usually starts and ends falsified, e.g. Newton's theory of motion originally was unable to describe the motion of the moon, and so by a falsificationist criteria it should have been disregarded almost immediately.  Yet this would have been a mistake because in fact Newtonian mechanics was able to explain the orbit of the moon eventually.

On the other hand, when Einstein's theory came in, the reason for it's support was because it effectively described the perihelion of Mercury, a prediction that Newton's theory got wrong and which came to be considered a falsification of Newton's theory (though we had been comfortable with the fact that Newton's theory couldn't explain Mercury's perihelion for several centuries before this).

It is taught by the hard sciences because the anti-dogmatic image it depicts is flattering, it is taught by the social sciences because they want to see themselves as like the hard sciences.