Explain how virtue has its origin in nature, free acts and God’s work.
Virtues are partly from outside and partly within according to St. Thomas and Aristotle. If virtues were only from outside the soul, they would be an imposition on nature; if they were wholly within, one would be innately virtuous. Since the either/or options fall short, the both/and is found to hold the answer. There are both seeds of virtue present in the intellect, will and the passions (natural tendencies in the soul) and these tendencies must be completed by free human choices.
Complete human integration requires willfully and freely choosing virtue. Without God’s grace, man can perfect himself in regards to good through human virtues. This is because those goods knowable by reason can be perfected through human efforts – these are acquired virtues. Acquired virtues are compatible with a sinful act since one act does not make or destroy a moral habit.
However, this is not the case with infused virtues. Divinely infused virtues are completely incompatible with mortal sin and are lost with even one mortal sin. Of the infused virtues, the theological virtues of faith, hope, and charity hold a special place because they are necessary for man to attain his end which is not attainable by nature alone. In regards to losing the theological virtues, one mortal sin would suffice as it is against charity. The loss of the virtue of charity does not result in an utter loss of faith and hope; they remain only an inchoate state.
In summation, virtue is a natural tendency within the soul and therefore not an imposition on nature; virtues are completed through free acts of the will choosing that which is in accord with reason and the good; man is called to an end by nature he cannot attain by nature because of the exalted character of the end and therefore needs the grace of Divinely infused virtues the chief of which are faith, hope, and charity.