Whether sin has an external cause?

❌ Objection 1 : It would seem that sin has no external cause. For sin is a voluntary act. Now voluntary acts belong to principles that are within us, so that they have no external cause. Therefore sin has no external cause.

❌ Objection 2 : Further, as nature is an internal principle, so is the will. Now in natural things sin can be due to no other than an internal cause; for instance, the birth of a monster is due to the corruption of some internal principle. Therefore in the moral order, sin can arise from no other than an internal cause. Therefore it has no external cause.

❌ Objection 3 : Further, if the cause is multiplied, the effect is multiplied. Now the more numerous and weighty the external inducements to sin are, the less is a man's inordinate act imputed to him as a sin. Therefore nothing external is a cause of sin.