1. Sin is from Good

71. To the other question, which was asked first [n.1], about the cause of sin, I say that sin, in the way in which it can have a cause, is from good.

72. The proof is that nothing is a ‘first evil’, otherwise it would lack the supreme perfection belonging to it; but that to which supreme perfection belongs is the supreme good in nature; therefore the supreme evil would be the supreme good in nature.

73. And upon this heresy [sc. there is a first, supreme evil] there follow many other unacceptable things, and not only against the faith but also against philosophy, because the heresy destroys itself and involves a contradiction; for a first evil would be a necessary existence and without partner and independent, if it were posited to be as equally a supreme first as the first good; being a necessary existence and without partner only belong to the most perfect entity.

74. So     therefore , in the way that evil has a cause, it can have no cause but good, speaking of the first created good.

75. This is plain from Augustine City of God 12.6, “He [who consents to the tempter] seems to have made for himself an evil will etc     .” Here Augustine seems to maintain that one’s own will is the cause of falling [sc. into sin], by its immoderate use of some created good - that is, a good that is in the power of the very will, so that just as the will itself can of itself use and not use, so it can enjoy immoderately and not enjoy immoderately some good agreeable to it; and thus this ‘first sin’ is immediately and first from the will alone.