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.

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

If we could sufficiently understand the order of the universe, we should find that it exceeds all the desires of the wisest men, and that it is impossible to make it better than it is, not only as a whole and in general but also for ourselves in particular, if we are attached, as we ought to be, to the Author of all, not only as to the architect and efficient cause of our being, but as to our master and to the final cause, which ought to be the whole aim of our will, and which can alone make our happiness.

If we were magically shrunk and put into someone's brain while she was thinking, we would see all the pumps, pistons, gears and levers working away and we would be able to describe the workings completely, in mechanical terms, thereby completely describing the thought processes of the brain. But that description would not contain any mention of thought! It would contain nothing but descriptions of pumps, pistons, levers!

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.

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

In whatever manner God created the world, it would always have been regular and in a certain general order. God, however, has chosen the most perfect, that is to say, the one which is at the same time the simplest in hypothesis and the richest in phenomena.