The thought of Alfred North Whitehead (1861–1947) is an exceptional phenomenon in post-Kantian philosophy of nature. Above all, it is authentically philosophical thought, decidedly different from any of the natural sciences. At the same time we here have to do with philosophical thought conducted not only in the context of highly developed classical physics, as was the case with Kant, but growing out of the great revolution which occurred in science at the turn of the twentieth century, the main element of which depended on the transition from classical to contemporary physics.