ABSTRACT
The physical universe for Descartes consists of one, infinitely extended, homogeneous, three-dimensional thing (Princ. ii 21-2: ‘indefinite’ is Descartes’s own preferred word for the kind of negative infinity involved). It has, and can have, no gaps in it; it follows that there cannot be a plurality of worlds, and any extended thing there is, is some local part of the one extended thing. There are, further, no ultimate atoms, or parts of matter which are ‘indivisible of their own nature’ (Princ. ii 20) – matter, in Descartes’s conception of it, has necessarily the geometrical property of being continuous. The truth in scientific atomism, according to Descartes, is merely that there are some small packets of the extended substance which travel around as a whole. This conception enables him to set up models of physical processes involving particles, but this means for him only matter moving, as it happens, in a particulate way, and does not involve items which are in any more fundamental way atoms.
