主题：【原创】判决性实验：从波普到拉卡托斯 -- 山一程

He undoubtedly says this because Fries had held that synthetic propositions a priori, or the First Principles of Demonstration, do not need to be proven. This follows from Hume and Kant's definition of "synthetic" (can be denied without contradiction) and from Aristotle's definition of "First Principles" (are not justified by derivation from other propositions). Since Popper thought that justification works through falsification, and never through verification, he obviously agreed that such propositions do not need to be proven in the sense of logical derivation. It is now common in science to use falsifiability as a criterion for dismissing theories or claims as parts of science. Popper's own critique of Marx and Freud as unfalsifiable was a classic study, and the salutary influence of the principle in discussion of psychics or astrology is occasionally seen.