In 1911, Alfred North Whitehead has a brainstorm: if we deny the reality of the instant, many problems of the philosophy of nature seem solved. His metaphysics, however, will wait until his moving to Harvard, in 1924, to mature. Besides his denial of the instants of time and the replacement of the concept of time by that of “process,” Whitehead articulates new concepts (concrescence, prehension) to account for the crystallization of successive empirical realities, the solidarity between events, the permanence of objects, and their deterministic behavior altogether. His views of nature fit well with both quantum mechanics and relativity theories, although not in the details of the latter. But one of his largely unnoticed merits, in my view, is to reopen the question of free will in the mind-body problem.