Philippe Lemoine in Nec Pluribus Impar:
Karl Popper famously defended the view, known as falsificationism, that what distinguishes science from non-science is falsifiability. On this view, a theory is scientific if and only if it’s falsifiable, at least in principle. What this means for a theory to be falsifiable is that one can think of a possible observation that would be inconsistent with the theory. For instance, since Newton’s law of universal gravitation implies that every particle exerts a force of attraction on every other particle, it would be falsified if we observed a particle that repels another particle. Since it’s at least conceivable that we could observe this, Newton’s law of universal gravitation is falsifiable and therefore scientific. Popper wants to contrast this with theories like psychoanalysis, which according to him can be reconciled with any conceivable observation, hence is not scientific.
I have often been struck, when talking to scientists, by the influence that Popper seems to have among them. I would go as far as saying that, in many scientific fields, falsificationism has become the official philosophy of science. It’s drummed into the heads of scientists when they’re in graduate school and, with a few exceptions, they never learn anything else about philosophy of science and spend the rest of their career thinking that Popper’s conception of science is still the gold standard. In fact, however, not only is falsificationism not the gold standard, but it never was.