He who hasn't tasted bitter things hasn't earned sweet things.

There are also two kinds of truths: truth of reasoning and truths of fact.

All the different classes of beings which taken together make up the universe are, in the ideas of God who knows distinctly their essential gradations, only so many ordinates of a single curve so closely united that it would be impossible to place others between any two of them, since that would imply disorder and imperfection. Thus men are linked with the animals, these with the plants and these with the fossils which in turn merge with those bodies which our senses and our imagination represent to us as absolutely inanimate.

In my judgment an organic machine new to nature never arises, since it always contains an infinity of organs so that it can express, in its own way, the whole universe; indeed, it always contains all past and present times.

[Alternate translation:] The Divine Spirit found a sublime outlet in that wonder of analysis, that portent of the ideal world, that amphibian between being and not-being, which we call the imaginary root of negative unity.

Reality cannot be found except in One single source, because of the interconnection of all things with one another. I maintain also that substances, whether material or immaterial, cannot be conceived in their bare essence without any activity, activity being of the essence of substance in general.

Nature does not make leaps.