Popper is known for his rejection of the classical inductivist views on the scientific method, in favour of empirical falsification: A theory in the empirical sciences can never be proven, but it can be falsified, meaning that it can and should be scrutinized by decisive experiments. He used the black swan fallacy to discuss falsification. If the outcome of an experiment contradicts the theory, one should refrain from ad hoc manoeuvres that evade the contradiction merely by making it less falsifiable. Popper is also known for his opposition to the classical justificationist account of knowledge, which he replaced with critical rationalism, "the first non-justificational philosophy of criticism in the history of philosophy."