Physics and philosophy are still known by the Greek names of the Greek intellectual pursuits from which they stem. However, in the seventeenth century they went through deep changes that have conditioned their further development and interaction right to the present day. In this chapter I shall sketch a few of the ideas and methods that were introduced at that time by Galileo, Descartes, and some of their followers, emphasizing those aspects that I believe are most significant for current discussions in the philosophy of physics.

Three reminders are in order before taking up this task.

First, in the Greek tradition, physics was counted as a part of philosophy (together with logic and ethics, in one familiar division of it) or even as the whole of philosophy (in the actual practice of “the first to philosophize” in Western Asia Minor and Sicily). Philosophy was the grand Greek quest for understanding everything, while physics or “the understanding of nature (physis)” was, as Aristotle put it, “about bodies and magnitudes and their affections and changes, and also about the sources of such entities” (De Caelo, 268a1–4). For all their boasts of novelty, the seventeenth-century founders of modern physics did not dream of breaking this connection. While firmly believing that nature, in the stated sense, is not all that there is, their interest in it was motivated, just like Aristotle's, by the philosophical desire to understand.