A monad is in one sense similar to the atoms of Democritus and yet more akin to the geometrical points of Pythagoras. Like atoms, monads are the ultimate indivisible elements of reality of which all material things are constituted. But they are not themselves either extended nor composed of matter. In a completely original thesis Leibniz holds that a monad is a psychological entity, which, when embodied in human beings, he calls ‘souls’.
