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

Even those who have the weakest souls could acquire absolute mastery over all their passions if we employed sufficient ingenuity in training and guiding them.

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

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

Intuition is the undoubting conception of a pure and attentive mind, which arises from the light of reason alone, and is more certain than deduction.

If we possessed a thorough knowledge of all the parts of the seed of any animal (e.g. man), we could from that alone, be reasons entirely mathematical and certain, deduce the whole conformation and figure of each of its members, and, conversely if we knew several peculiarities of this conformation, we would from those deduce the nature of its seed.

Variant: When it is not in our power to follow what is true, we ought to follow what is most probable.