Metaphysics is universal and is exclusively concerned with primary substance. ... And here we will have the science to study that which is, both in its essence and in the properties which it has.
First, have a definite, clear practical ideal; a goal, an objective. Second, have the necessary means to achieve your ends; wisdom, money, materials, and methods. Third, adjust all your means to that end.
Salt water when it turns into vapour becomes sweet, and the vapour does not form salt water when it condenses again. This I know by experiment. The same thing is true in every case of the kind: wine and all fluids that evaporate and condense back into a liquid state become water. They all are water modified by a certain admixture, the nature of which determines their flavour.
Anger is always concerned with individuals, ... whereas hatred is directed also against classes: we all hate any thief and any informer. Moreover, anger can be cured by time; but hatred cannot. The one aims at giving pain to its object, the other at doing him harm; the angry man wants his victim to feel; the hater does not mind whether they feel or not.
While most of those who hold that the whole heaven is finite say that the earth lies at the center, the philosophers of Italy, the so-called Pythagoreans, assert the contrary. They say that in the middle there is fire, and that the earth is one of the stars, and by its circular motion round the center produces night and day.
In all things which have a plurality of parts, and which are not a total aggregate but a whole of some sort distinct from the parts, there is some cause.
[the virtues] cannot exist without Prudence. A proof of this is that everyone, even at the present day, in defining Virtue, after saying what disposition it is [i.e. moral virtue] and specifying the things with which it is concerned, adds that it is a disposition determined by the right principle; and the right principle is the principle determined by Prudence.
All art is concerned with coming into being; for it is concerned neither with things that are, or come into being by necessity, nor with things that do so in accordance with nature.