In the second edition of Hermann Cohen’s Kant’s Theory of Experience, he abandons the interpretation of Kant’s Anticipations of Perception that he gave in the first edition, in favourof a radically different one. On his early interpretation, the Anticipations is largely of psychological interest for its influence on, and continuing significance for, physiological psychology and psychophysics. But on his mature interpretation, it defends the superiority of a dynamic conception of nature over a mechanical conception. Further, on his early interpretation, Cohen (...) thought the Anticipations was not a central part of Kant’s critical theory of knowledge. But on his mature interpretation, he thinks it is absolutely central to that project. What is more, Cohen seems to have revised his interpretation in a relatively short period of time, in 1880-1. This paper argues that Cohen’s change in views about Kant’s Anticipations is explained by his reception of Leibniz in the very early 1880s, and specifically Cohen’s reception of Leibniz’s arguments against Descartes’ view that extension is the essence of matter. (shrink)