Each problem that I solved became a rule, which served afterwards to solve other problems.

I hope that posterity will judge me kindly, not only as to the things which I have explained, but also to those which I have intentionally omitted so as to leave to others the pleasure of discovery.

There is a great difference between mind and body insomuch as body is by nature always divisible, and the mind is entirely indivisible.

An optimist may see a light where there is none, but why must the pessimist always run to blow it out?

Before examining this more carefully and investigating its consequences, I want to dwell for a moment in the contemplation of God, to ponder His attributes in me, to see, admire, and adore the beauty of His boundless light, insofar as my clouded insight allows. Believing that the supreme happiness of the other life consists wholly of the contemplation of divine greatness, I now find that through less perfect contemplation of the same sort I can gain the greatest joy available in this life.

I concluded that I might take as a general rule the principle that all things which we very clearly and obviously conceive are true: only observing, however, that there is some difficulty in rightly determining the objects which we distinctly conceive.

Every man is indeed bound to do what he can to promote the good of others, and a man who is of no use to anyone is strictly worthless.