147. The intellectual virtues, except prudence, are not perfect virtues, since, While they make an act good, they do not necessarily make the agent good. A man may have great knowledge about morality, or be able to produce excellent works of art, and at the same time be not virtuous, or have no love for his work.
148. Prudence is an intellectual virtue, since it resides in the intellect; but it is also classed among the moral virtues, since its object is the direction of human acts to their right end.
149. The moral virtues are those habits that perfect the will and the sensitive appetite with reference to their immediate and respective objects; that is, they are habits concerned with acts as means to the Last End. They make the act good, and make good also him who performs it; and they are thus superior as virtues to the intellectual habits.
150. There are four principal moral virtues: (a) in the intellect there is prudence, which guides all the actions and passions by directing the other moral virtues to what is good according to reason; (b) in the will there is justice, which inclines a person to make his actions accord with what he owes to others; (c) in the irascible appetite is fortitude, which subjects to reason the passions that might withdraw from good, such as fear of dangers and labors; (d) in the concupiscible appetite is temperance, which represses the motions of passions that would impel one to some sensible good opposed to reason.
These four virtues are also called cardinal virtues, because all the other moral virtues hinge on them.
151. The theological virtues are those that perfect the intellect and the will with reference to God, their ultimate, supernatural object. They are three: (a) faith, which is a virtue infused into the intellect, giving man supernatural truths that are perceived by a divine light; (b) hope, which is a virtue infused into the will, enabling man to tend towards the supernatural destiny disclosed by faith as towards an end possible of attainment; (c) charity, which is a virtue infused into the will, uniting man’s affections to the object of his hope and transforming him into its likeness.
152. Causes of Virtues.—The causes of virtue are three: (a) nature, which is the cause of the inchoative intellectual and moral virtues, that is, of the theoretical and practical principles that are naturally known, and of the inclinations to virtue that arise from an individual’s bodily constitution; (b) practice, which is the cause of perfected intellectual and moral virtues, that is, of the good habits that are formed by repeated acts (e.g., knowledge obtained through study, temperance fixed in the character through continued effort); (c) infusion from on high, which is the cause of the virtues that surpass nature (i.e., of the theological virtues and of the moral virtues that are concerned with our acts as ordered to the supernatural).
153. Properties of the Virtues.—From the definition of virtue given above certain properties result.
(a) Since a virtue makes conduct agree with a certain fixed standard, it does not allow of excess or defect. Hence, virtue follows the golden mean.
(b) Since the other moral virtues would go to extremes without the guidance of prudence, and since prudence would not judge aright without the right dispositions of the other virtues, it follows that the four moral virtues, at least in their perfect state, must always be together. And because charity is the fulfillment of the whole law, he who has charity has also all the other infused virtues.