“The words ‘Here you can find perfect peace’ can be written only over the gates of a cemetery.”

There is nothing without reason.

I also take it as granted that every created thing, and consequently the created monad also, is subject to change, and indeed that this change is continual in each one.

There is a world of created beings – living things, animals, entelechies, and souls – in the least part of matter. Thus there is nothing waste, nothing sterile, nothing dead in the universe; no chaos, no confusions, save in appearance.

Make me the the master of education, and I will undertake to change the world.

There is no way in which a simple substance could begin in the course of nature, since it cannot be formed by means of compounding.

In symbols one observes an advantage in discovery which is greatest when they express the exact nature of a thing briefly and, as it were, picture it; then indeed the labor of thought is wonderfully diminished.

When God works miracles, he does not do it in order to supply the wants of nature, but those of grace. Whoever thinks otherwise, must needs have a very mean notion of the wisdom and power of God.

Although the whole of this life were said to be nothing but a dream and the physical world nothing but a phantasm, I should call this dream or phantasm real enough, if, using reason well, we were never deceived by it.

Now this connection or adaption of all created things with each, and of each with all the rest, means that each simple substance has relations which express all the others, and that consequently it is a perpetual living mirror of the universe.

One cannot explain words without making incursions into the sciences themselves, as is evident from dictionaries; and, conversely, one cannot present a science without at the same time defining its terms.

There is nothing waste, nothing sterile, nothing dead in the universe; no chaos, no confusions, save in appearance.

The greatness of a life can only be estimated by the multitude of its actions. We should not count the years, it is our actions which constitute our life.

Our reasonings are grounded upon two great principles, that of contradiction, in virtue of which we judge false that which involves a contradiction, and true that which is opposed or contradictory to the false.

Music is a secret and unconscious mathematical problem of the soul.

Every mind has a horizon in respect to its present intellectual capacity but not in respect to its future intellectual capacity.

He who understands Archimedes and Apollonius will admire less the achievements of the foremost men of later times.