Not a scientific one, but a mathematical one: Hypothesis testing. Statistics inverts your thinking, because it asks you to only tentatively accept every singl

Not a scientific one, but a mathematical one: Hypothesis testing. Statistics inverts your thinking, because it asks you to only tentatively accept every single conclusion you make ("fail to reject"). All science rests on this, the twinned ideas that 1) something must be testable for it to be useful and 2) it is only through embracing uncertainty (it _is_ possible for a coin flipped 50 times to come up heads 50 times) that one can mediate certainty.