Whether Original Sin is Desire
We proceed to the third article thus:
1. It seems that original sin is not desire. For every sin is contrary to nature, as the Damascene says (2 De Fid. Orth.4, 30). But desire is in accordance with nature, since it is the proper act of the power of concupiscence, which is a natural power. It follows that desire is not original sin.
2. Again, the apostle says that original sin is responsible for the |passions of sin| that are in us (Rom.7:5). But there are many passions besides desire, as was said in Q.23, Art.4. Hence original sin is not desire rather than any other passion.
3. Again, it was said in Art.2 that all parts of the soul are deranged by original sin. Now the chief part of the soul is the intellect, as the philosopher explains in 10 Ethics 7. Original sin is therefore ignorance, rather than desire.
On the other hand: Augustine says (1 Retract.15): |Desire is the guilt of original sin.|
I answer: the species of each thing depends on its formal nature. Now we said in the preceding article that the species of original sin is determined by its cause. The formal nature of original sin is therefore determined by the cause of original sin. We must understand the cause of original sin, however, in contrast to the cause of the original justice which is its opposite, the causes of opposites being themselves opposites. The whole order of original justice consisted in the subjection of man's will to God. Man was subject to God first and foremost through his will, which directs all other parts of his soul to their end, as we said in Q.9, Art.1. Disorder in any other part of his soul is therefore the consequence of his will turning away from God. Privation of original justice, by which the will of man was subject to God, is therefore the formal element in original sin. Every other disorder of the powers of the soul is related to original sin as the material which it affects. Now the disorder of these other powers consists especially in this, that they are wrongly directed to changeable good. Such disorder may be called by the common name of |desire.| Materially, then, original sin is desire. Formally, it is the lack of original justice.
On the first point: in man, the power of desire is naturally ruled by reason. Desire is therefore natural to man in so far as it is subject to reason. But desire which exceeds the bounds of reason exists in him as something contrary to nature. Such is the desire of original sin.
On the second point: we said in Q.25, Art.1, that the passions of anger are reducible to the passions of desire, which are more fundamental, and in Q.25, Art.2, that desire itself moves us more vehemently than any other of these latter passions, and is felt more. Original sin is accordingly ascribed to desire, since it is more fundamental than other passions, and virtually includes all of them.
On the third point: intellect and reason have the primacy where good in concerned. But, conversely, the lower part of the soul comes first where evil is concerned. For it darkens reason and drags it down, as we said in Q.80, Art.1. Original sin is therefore said to be desire rather than ignorance, although ignorance is one of its material defects.