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.

There are two famous labyrinths where our reason very often goes astray. One concerns the great question of the free and the necessary, above all in the production and the origin of Evil. The other consists in the discussion of continuity, and of the indivisibles which appear to be the elements thereof, and where the consideration of the infinite must enter in.

It is worth noting that the notation facilitates discovery. This, in a most wonderful way, reduces the mind's labour.

Indeed every monad must be different from every other. For there are never in nature two beings, which are precisely alike, and in which it is not possible to find some difference which is internal, or based on some intrinsic quality.

It's easier to be original and foolish than original and wise.

The knowledge which we have acquired ought not to resemble a great shop without order, and without an inventory; we ought to know what we possess, and be able to make it serve us in need.

If you have a clear idea of a soul, you will have a clear idea of a form; for it is of the same genus, though a different species.