The seventeenth-century philosopher Leibniz is famous, as the author of a system of metaphysics so grand and abstract that Kant called it ‘a kind of enchanted world’, Hegel ‘a metaphysical romance’ and Bertrand Russell ‘a fantastic fairy tale’. As a mathematician, Leibniz held that a formula could always be found to describe, explain and give a pattern for any set of points, however randomly they had been set down. Leibniz argues that ‘always, in every true proposition, necessary or contingent, universal or particular, the concept of the predicate is in a sense included in that of the subject; the predicate’ ‘is present in the subject’. Leibniz applies his doctrine of the predicate being in the subject to individual substances. A connection between Leibniz’s mathematical idea of substance as a point and his psychological idea of substance as a mind is made in his view that a mind is itself a point.