One may go wrong in many different ways, but right only in one, which is why it is easy to fail and difficult to succeed.

In inventing a model we may assume what we wish, but should avoid impossibilities.

The body is at its best between the ages of thirty and thirty-five.

These two rational faculties may be designated the Scientific Faculty and the Calculative Faculty respectively; since calculation is the same as deliberation, and deliberation is never exercised about things that are invariable, so that the Calculative Faculty is a separate part of the rational half of the soul.

[I]t is rather the case that we desire something because we believe it to be good than that we believe a thing to be good because we desire it. It is the thought that starts things off.

Prosperity makes friends and adversity tries them. A true friend is one soul in two bodies

Revolutions are effected in two ways, by force and by fraud.