 For Diderot, there is only one substance and it is material. Here, he is loosely aligned with Spinoza. But this substance is in perpetual flux (a more Lucretian element in his thought), so that the individual beings we encounter are merely temporary, provisional clusters of molecules in interaction with one another, in the midst of what he terms the general “vicissitude” of the cosmos (by which he means its change). In the entry “Immuable” (“Immutable”) he writes that “Nature is in a state of perpetual vicissitude. It follows from the general law of all bodies: either they are in motion, or they tend to be in motion” (Enc. VIII: 577).