I have said more than once, that I hold space to be something purely relative, as time; an order of coexistences, as time is an order of successions.

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.

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

We should like Nature to go no further; we should like it to be finite, like our mind; but this is to ignore the greatness and majesty of the Author of things.

Reality cannot be found except in One single source, because of the interconnection of all things with one another.

To love is to take delight in happiness of another, or, what amounts to the same thing, it is to account another's happiness as one's own.

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.