Leibniz and Sleigh on Substantial Unity

This essay examines the basis of Leibniz’s views on the unity of corporeal substance. It draws on the analysis of Robert Sleigh, who linked the unity of Leibnizian substances to their possession of identity through change. It argues that Sleigh’s analysis leaves many questions about unity unanswered, notably the problem of how a substantial form produces unity in its associated passive principle or body, whose components are in constant flux. The key to this problem lies in a historically informed account of Leibniz’s writings, which reveal his underlying assumptions on unity.