God and nature create nothing that does not fulfill a purpose

The End is included among goods of the soul, and not among external goods.

Thus it is thought that justice is equality; and so it is, but not for all persons, only for those that are equal. Inequality also is thought to be just; and so it is, but not for all, only for the unequal. We make bad mistakes if we neglect this for whom when we are deciding what is just. The reason is that we are making judgements about ourselves, and people are generally bad judges where their own interests are involved.

...we are all inclined to ... direct our inquiry not by the matter itself, but by the views of our opponents; and, even when interrogating oneself, one pushes the inquiry only to the point at which one can no longer offer any opposition. Hence a good inquirer will be one who is ready in bringing forward the objections proper to the genus, and that he will be when he has gained an understanding of the differences.

And yet the true creator is necessity, which is the mother of invention.

In a race, the quickest runner can never overtake the slowest, since the pursuer must first reach the point whence the pursued started, so that the slower must always hold a lead.

For suppose that every tool we had could perform its task, either at our bidding or itself perceiving the need, and if-like the statues made by Dædalus or the tripods of Hephæstus, of which the poet says that "self-moved they enter the assembly of the gods" - shuttles in a loom could fly to and fro and a plectrum play a lyre all self-moved, then master-craftsmen would have no need of servants nor masters of slaves.