Discourse on Metaphysics (Leibniz)

Leibniz, G. W. Discourse on Metaphysics and Other Essays. Indianapolis, IN: Hackett, 1991.

These short essays introduce the reader to Leibniz’s so-called “Perfect Being Theology.” Imagine if Anselm had invented Calculus and that’s what you get with Leibniz. Not all of his arguments work (as they stand), but all are interesting and worth interacting with.

Leibniz begins by defining power and knowledge and perfections, and so they don’t have limits. A perfect being must occupy the least volume, which means it/He is a mind.

Leibniz says a soul (maybe a monad, as we will see later on), like a proposition, says the predicate must be contained virtually in the subject. That’s true for propositions, but how does it work with souls? Leibniz says that there are vestiges in X’s soul of everything that has happened to him and traced of everything that happens in the universe. Fascinating. I don’t know that’s true. As a traducianist, I agree with the first half of the proposition.

On Substances

A substance “is like a complete world and like a mirror of God or the whole universe” (Leibniz 9). Don’t read “world” too literally. He means something akin (though not identical with) Plantinga’s view of possible worlds.

Leibniz also breaks new ground on “necessary” vs. contingent truths (13). In short, nothing is necessary whose contrary is possible.

His talk on “souls” is interesting, if underdeveloped. He says we have a quality of our soul that expresses “some nature, form, or essence” of a thing which is properly the idea of a thing (29). The expression in our soul is the idea of a thing. Our idea of the idea is the concept of the thing.

Principle of Sufficient Reason

This is Leibniz’s argument for the existence of God:
1) No single individual thing has the entire collection or set of things in it.
2) This set of things is a sufficient reason for existence.
3) All states of things are copied from the previous state.
4) Essence strives for existence
5) An eternal truth (like an equation) cannot derive its necessary existence from contingent things
6) Therefore, there must be an absolute subject to ground this existence.

Preface to New Essays

Leibniz notes that Newton is closer to Aristotle while he is closer to Plato. Leibniz refutes the supposedly scholastic dictum that knowledge can’t be in the intellect until it is first in the senses. Mathematics, for example, relies on numerous assumptions which can’t be reduced to sense experience. Moreover, if the soul is a tabula rasa, then my soul at birth would be identical to any other soul at birth, since every soul is blank.


1) A monad is a simple substance that enters into composites.
2) Monads contain their own entelechies
3) Everything exists in a plenum (chain of being). Leibniz doesn’t make the connection but it must have been in his mind: how does his work on the infinitesimal calculus factor here?

This text is an excellent introduction to the man who co-discovered calculus.


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