 But perhaps he did present all the elements of these matters, though in improper, hence inadequate, order. The obvious place to look for such a presentation is in the so-called “Physical Interlude” (hereinafter PI) following IIp13s, in which Spinoza gives his most extended and detailed discussion of his own views about the nature of bodies and their principles of distinction and individuation. But the PI seems to offer little  help.[6]  First, at least at the time of letter 83, Spinoza thought that what was needed to help explain variety in matter was an appeal to an attribute that expresses infinite and eternal essence. Yet the text of the PI makes no appeal to the infinitude, eternality or expressive nature of extension or any other attribute. More importantly, at least on the face of it, the account of the individuation of bodies presented in the PI moves in much the same futile circle as that offered by Descartes. That motion serves to individuate bodies is quite explicit in PIDL1: “Bodies are distinguished from one another by reason of motion and rest, speed and slowness.” PID5 goes on to define “body, or Individual”, in terms of motion, and in a way that presupposes a plurality of bodies: