I am indeed amazed when I consider how weak my mind is and how prone to error.

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

The principal effect of the passions is that they incite and persuade the mind to will the events for which they prepared the body.

The only thing we have power over in the universe is our own thoughts.

Neither the true nor the false roots are always real; sometimes they are imaginary; that is, while we can always imagine as many roots for each equation as I have assigned, yet there is not always a definite quantity corresponding to each root we have imagined.

We never understand a thing so well,and make it our own, as when we have discovered it for ourselves.

Good sense is, of all things among men, the most equally distributed; for every one thinks himself so abundantly provided with it, that those even who are the most difficult to satisfy in everything else, do not usually desire a larger measure of this quality than they already possess.