Harmony as a Criterion of Contingent Truth in Leibniz

Strong phenomenalist readings of Leibniz take him to have thought the reality of bodies consists in the mutual harmony of the monads’ representations of them. I argue that Leibniz ought not to be read as a strong phenomenalist: the text does not force such a reading upon us, and there are systematic reasons to avoid such a reading. Since the systematic reasons in question are well-documented in the literature, I focus on the task of showing that textual evidence for the strong phenomenalist reading is sparse. I work toward this task in two ways. First, I argue that the Harmony Principle (the principle that there is a close relationship between the reality of bodies and the mutual harmony of the monads’ perceptions of them), traditionally taken as evidence of Leibniz’s commitment to strong phenomenalism, is more naturally read as an epistemic principle. Second, I argue that Leibniz’s repeated identification of bodies with phenomena is equally amenable to a weaker reading of him as a moderate phenomenalist, who thought bodies owe their unity to perception. The failure to distinguish between moderate and strong phenomenalism in the literature has led proponents of the strong phenomenalist reading to take any passages where such identity claims occur as evidence for their reading. But such claims, unlike the strong phenomenalist thesis, are reconcilable with Leibniz’s aggregate conception of body, which, (1) characterizes bodies as phenomena owing their unity to perception, but (2) takes the reality of bodies to be “borrowed” from their underlying monads.