The first problem, dealt with in chs. 1—4, is the matter of division, which is related mainly to the natural life of the soul. The second problem, dealt with in ch. 5, the second section of the book, is the sin of fornication, which is related to the lust of the flesh. This problem, involving incest with one's stepmother, is morally more gross than the former. The former pertains to the strife that comes from pride; the latter is a gross sin that comes from lust.