The fundamental principle of Leibniz's idealism is that “there is nothing in things except simple substances, and in them perception and appetite.” He held that bodies are not simple, and therefore must be constructed out of the simple, perceiving substances. He held indeed that bodies are aggregates of substances, and also that they are merely phenomena (i.e., appearances). Leibniz's consistency and constancy in holding these two theses are defended in this chapter against highly influential objections. It considers in what sense he regarded bodies as phenomena (and in what sense as real), and why he thought their being aggregates of substances a reason for rather than against counting them as phenomena.
Keywords: aggregates, appetite, appearances, bodies, idealism, Leibniz, perception, phenomena, simple substances