Doubt is the origin of wisdom

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.

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.

If I simply refrain from making a judgment in cases where I do not perceive the truth with sufficient clarity and distinctness, then it is clear that I am behaving correctly and avoiding error.

There is nothing more ancient than the truth.

If I go for the alternative which is false, then obviously I shall be in error; if I take the other side, then it is by... chance that I arrive at the truth, and I shall still be at fault.... In this incorrect use of free will may be found the privation which constitutes the essence of error.

Instead I ought to be grateful to Him who never owed me anything for having been so generous to me, rather than think that He deprived me of those things or has taken away from me whatever He did not give me.