Principles of Nature and GraceGottfried Wilhelm Leibniz

Leibniz wrote this short treatise in 1714, the same year as the Monadology, and it covers much of the same ground in a more accessible style. The work summarizes his metaphysics for a non-specialist audience: the doctrine that reality consists of simple substances (monads), each of which mirrors the entire universe from its own point of view.

Monads are the true atoms of nature. They have no parts, no extension, no shape. Each monad perceives the whole universe, but with varying degrees of clarity. Bare monads perceive confusedly; animal souls perceive with sensation and memory; rational spirits perceive with reason and self-consciousness. The hierarchy of beings is a hierarchy of perception.

The treatise culminates in the question that Leibniz considered the most fundamental in all of philosophy: "Why is there something rather than nothing?" The answer requires a sufficient reason outside the series of contingent things, and that reason is God, who chooses to create the best of all possible worlds. Every monad, every event, every apparent evil finds its justification in the perfection of the whole. The brevity of the work belies its scope: in fewer than twenty pages, Leibniz attempts to explain everything.