3. Scotus’ own Solution

46. I concede, then, according to the preceding solution of the question [n.33], that sin is a corruption of rightness in second act, and not of natural rightness or of any habitual rightness but of actual moral rightness. But I do not understand the corruption to be that which is a change from being to non-being (for sin can remain after such a change of justice from being to non-being, and can also be present without such change from being to non-being); but I understand the corruption formally, the way privation is said to be formally the corruption of its opposed positive; for in this way the idea of sin is formally the corruption of rightness in second act, because it is opposed to that rectitude as a privation is opposed to its positive; not opposed, to be sure, to a rectitude that is present (because then two opposites would be present at once), nor to a rectitude that was first there in the act (because in order for there to be a change from opposite to opposite no act remains), but to a rectitude that should have been present.

47. For free will is duty bound to elicit all its acts in conformity with a higher rule, namely in accord with divine precept; and so, when it acts against conformity to this rule, it lacks the actual justice that is due (that is, the justice which should have been present in the act and is not present [n.51]); this lack, to the extent it is the act of a deficient will (as shall be said in one of the solutions [n.125]), is formally actual sin.

48. This is clear from authorities:

The first is from Augustine On the Two Souls ch.11 n.15, “Sin is the will to keep or pursue what justice forbids, and from which it is free to abstain;” this is to say in brief: sin is willing something forbidden, so that the will there is the material element (and to this extent the whole is attributed to the will, because the whole is in the will’s power) and the thing forbidden or prohibited is the formal element, because it signifies the disagreement with a higher rule.

49. Ambrose similarly in his book On Paradise ch.8 n.39 (and it is in the Master’s text), “Sin is transgression of heavenly commands etc.”

50. With this agrees what Augustine says City of God 12.8, “The will is made bad in that which would not happen if the will did not will it; and so voluntary failings are followed by just punishment. For the will falls not toward bad things but in a bad way, that is, not toward bad natures but for this reason in a bad way, that it falls against the order of natures from that which is highest toward that which is lower... And thereby he who perversely loves the good of any nature...becomes bad and wretched in a good thing, having been deprived of a better.” It as if he were to say: the positive act of willing a creature is not sin formally, but lack of due order in the act is, an act in which the created good should be loved for the sake of the supreme good - and the will fails of this order by resting in a created good; and this failing is formally sin.

51. With these authorities [nn.48-50] reason agrees, because every sin is formally injustice, and sin of this sort is injustice of this sort and consequently is a privation of justice of this sort [dd.30-32 n.51]; therefore actual sin is formally actual injustice, so it is privation of actual justice, that is, of the justice that should have been present in the act.