There are also two kinds of truths, those of reasoning and those of fact. Truths of reasoning are necessary and their opposite is impossible, and those of fact are contingent and their opposite is possible. When a truth is necessary its reason can be found by analysis, resolving it into more simple ideas and truths until we reach those which are primitive.

Now, as there is an infinity of possible universes in the Ideas of God, and as only one of them can exist, there must be a sufficient reason for God's choice, which determines him toward one rather than another. And this reason can be found only in the fitness, or the degrees of perfection, that these worlds contain, since each possible thing has the right to claim existence in proportion to the perfection it involves.

Every present state of a simple substance is the natural consequence of its preceding state, in such a way that its present is big with its future.

The present is great with the future.

Music is nothing but unconscious arithmetic.

It is God who is the ultimate reason things, and the Knowledge of God is no less the beginning of science than his essence and will are the beginning of things.

I hold that it is only when we can prove everything we assert that we understand perfectly the thing under consideration.