In this paper I will discuss the doctrine of substance which emerges from Leibniz’s unpublished early memoir De affectibus of 1679. The memoir marks a new stage in Leibniz’s views of the mind. The motivation for this change can be found in Leibniz’s rejection of the Cartesian theory of passion and action in the 1670s. His early Aristotelianism and some features of Cartesianism persisted to which Leibniz added influences from Hobbes and Spinoza. His nascent dynamical concept of substance is seemingly (...) a combination of old and fresh influences, representing a characteristically eclectic approach, but I will argue that the influence of Hobbes is especially important in the memoir. To do that, I will examine Leibniz’s development in the 1670s up to the De affectibus and consider the nature of affects in the memoir, especially the first affect which starts the thought sequence. This first affect of pleasure or pain is the key to Leibniz’s theory of active substances and in this way to the whole of Leibniz’s moral psychology and ethical metaphysics. (shrink)