If there were some solitary or feral man, the passions of the soul would be sufficient for him; by them he would be conformed to things in order that he might have knowledge of them. But because man is naturally political and social, there is need for one man to make his conceptions known to others, which is done with speech. So significant speech was needed if men were to live together. Which is why those of different tongues do not easily live together.

It is a sin directly against one's neighbour, since one man cannot over-abound in external riches, without another man lacking them.

It must be understood that prime matter, and form as well, is neither generated nor corrupted, because every generation is from something to something. Now that from which generation proceeds is matter, and that to which it proceeds is form. So that, if matter or form were generated, there would be a matter for matter and a form for form, endlessly. Whence, there is generation only of the composite, properly speaking.

I receive Thee ransom of my soul. For love of Thee have I studied and kept vigil toiled preached and taught.

Given the sin of impiety through which they [the Romans] sinned against the divine nature [by idolatry], the punishment that led them to sin against their own nature followed.... I say, therefore, that since they changed into lies [by idolatry] the truth about God, He brought them to ignominious passions, that is, to sins against nature; not that God led them to evil, but only that he abandoned them to evil.

A man does not always choose what his guardian angel intends.

A scrap of knowledge about sublime things is worth more than any amount about trivialities.