1. THE DOCTRINE OF MONADS.—The fundamental peculiarity of Leibnitz’s theory is its opposition to Spinozism. Substance, as the indeterminate universal, was with Spinoza the only positive. With Leibnitz also the conception of substance lay at the basis of his philosophy, but his definition of it was entirely different. While Spinoza had sought to exclude from his substance every positive determination, and especially all acting, and had apprehended it simply as pure being, Leibnitz viewed it as living activity and active energy, an example for which might be found in a stretched bow, which moved and straightened itself through its own energy as soon as the external hindrance was removed. That this active energy forms the essence of substance is a principle to which Leibnitz ever returns, and from which, in fact, all the other chief points in his philosophy may be derived. From this there follow at the outset two determinations of substance directly opposed to Spinozism; first, that it is a single being, a monad; and second, that there are a multiplicity of monads. The first follows because substance, in so far as it exercises an activity similar to an elastic body, is essentially an excluding activity, or repulsion; the conception of an individual or a monad being that which excludes another from itself. The second follows because the existence of one monad involves the existence of many. The conception of one individual postulates other individuals, which stand over against the one as excluded from it. Hence the fundamental thesis of the Leibnitz philosophy in opposition to Spinozism is this, viz., there is a multiplicity of individual substances or monads.