Abstract

For Leibniz, it was a requirement upon the `fundamentally real' to have a `principle of unity'. What does this mean?One general point is that Substance cannot be understood as pure extension. But there is a particular point about cohesion: a real thing had to have some means by which its parts were stuck together. But Leibniz' insistence on `unity' is also an insistence on indivisibility. Under this head there is first the point that there appears to be a contradiction between extension and being incapable of being cut in two. Second, Leibniz uses the notion of `indivisibility' to mark the following distinction among things made up of parts: those which cannot be split without being destroyed; and the rest . To be `indivisible' is to be of the first type. Leibniz' insistence that the truly real must be `indivisible' is then his insistence that the truly real, if it is made up of parts, must be a thing with `integrity', i.e. not an aggregate.What does Leibniz think of as the connection between what is truly real and the possession of `integrity'? He took from Scholasticism the doctrine that action is necessarily attributed to a substance having `integrity', contructing what was in effect a theory of action with two parts: only self-subsistent substances can act; and an action is an origination of change. Leibniz thus insists that self-subsistent substances must be indivisible, in the sense that they cannot be mere aggregates. Aggregates cannot act, and self-subsistence in effect is the capacity for action. This is the most fundamental reason Leibniz had for insisting that the truly real must have a `principle of unity'.It is misleading to speak of Leibniz reintroducing the Scholastic form-and-matter conception of substance for the following reasons: the Scholastic `form' precisely lacked a `principle of action'; and during the period when it is suggested that Leibniz' conception was essentially Scholastic he was defending the view that what his `form' informed was not matter at all but what he called a `metaphysical point'