AMONG STUDENTS OF HIS SYSTEM, the relationship between Leibniz's dynamics and his metaphysics has long been a subject of intense interest and dispute. For Anglo-American scholars of this century, the early tone was set by Bertrand Russell's rather grim assessment" that the relation of Leibniz's Dynamics to his Metaphysics is hopelessly confused, and that the one cannot stand while the other is maintained.''~ As Russell saw it, Leibniz's commitment to the noncommunication thesis--the metaphysical thesis that, strictly speaking, created substances are not capable of causal interaction'--could not be reconciled with the obvious demand, in the science of dynamics, to understand physical phenomena in terms of a genuine causal interaction among material particles:" Even when a thing is defined as one causal series," Russell argued, we can hardly escape the admission, which however is directly self-contradictory, that things do, after all, interact.

And this is, in fact, admitted practically in Leibniz's writings. Although Dynamics requires us to assign causal action to each piece of matter, it requires us, just as much, to take account of all material particles in discussing what will happen to any one. That is, we require, on a purely dynamical basis, to admit transeunt action, the action of one thing on another. This was not avoided by Leibniz: on the contrary, the purely material