5. Thus we have the four cardinal virtues: prudence, a habit of the intellect; temperance, a habit of the concupiscible appetite; fortitude, a habit of the irascible appetite; and justice, a habit of the will. Temperance and Fortitude in the Home Department; Justice for Foreign Affairs; with Prudence for Premier. Or, to use another comparison, borrowed from Plato, prudence is the health of the soul, temperance its beauty, fortitude its strength, and justice its wealth.
Readings.—St. Thos., 1a 2æ, q. 61, art. 2, in corp.; ib., q. 56, art. 4, in corp., ad 1-3; ib., q. 56, art. 6, in corp., ad 1, 3; ib., q. 59, art. 4, in corp., ad 2; Plato, Laws, 631 B, C.
SECTION VI.—Of Prudence.
1. Prudence is right reason applied to practice, or more fully it may be defined, the habit of intellectual discernment that enables one to hit upon the golden mean of moral virtue and the way to secure that mean. Thus prudence tells one what amount of punishment is proper for a particular delinquent, and how to secure his getting it. It is to be observed that prudence does not will the golden mean in question, but simply indicates it. To will and desire the mean is the work of the moral virtue concerned therewith: as in the case given it is the work of vindictive justice.
2. From the definition of moral virtue above given (c. v., s. iv., n. 4, p. 79), it is clear that no moral virtue can come into act without prudence: for it is the judgment of the prudent man that must define in each case the golden mean in relation to ourselves, which every moral virtue aims at. Thus, without prudence, fortitude passes into rashness, vindictive justice into harshness, clemency into weakness, religion into superstition.
3. But may not one with no prudence to guide him hit upon the golden mean by some happy impulse, and thus do an act of virtue? We answer, he may do a good act, and if you will, a virtuous act, but not an act of virtue, not an act proceeding from a pre-existent habit in the doer. The act is like a good stroke made by chance, not by skill; and like such a stroke, it cannot be readily repeated at the agent's pleasure. (See c. v., s. i., n. 4, p. 66; and Ar., Eth., II., iv., 2.)
4. Prudence in its essence is an intellectual virtue, being a habit resident in the understanding: but it deals with the subject-matter of the moral virtues, pointing out the measure of temperance, the bounds of fortitude, or the path of justice. It is the habit of intellectual discernment that must enlighten every moral virtue in its action. There is no virtue that goes blundering and stumbling in the dark.
5. He is a prudent man, that can give counsel to others and to himself in order to the attainment of ends that are worthy of human endeavour. If unworthy ends are intended, however sagaciously they are pursued, that is not prudence. We may call it sagacity, or shrewdness, being a habit of ready discernment and application of means to ends. Napoleon I. was conspicuous for this sagacity. It is the key to success in this world. But prudence discovers worthy ends only, and to them only does it provide means. The intellect is often blinded by passion, by desire and by fear, so as not to discern the proper end and term to make for in a particular instance and a practical case. The general rules of conduct remain in the mind, as that, "In anger be mindful of mercy:" but the propriety of mercy under the present provocation drops out of sight. The intellect does not discern the golden mean of justice and mercy in relation to the circumstances in which the agent now finds himself. In other words, the habit of prudence has failed; and it has failed because of the excess of passion. Thus prudence is dependent on the presence of the virtues that restrain passion, namely, fortitude and temperance. A like argument would hold for the virtue of justice, that rectifies inordinate action in dealing with another. The conclusion is, that as the moral virtues cannot exist without prudence, so neither can prudence exist without them: for vice corrupts the judgment of prudence.
6. Hence we arrive at a settlement of the question, whether the virtues can be separated, or whether to possess one is to possess all. We must distinguish between the rudimentary forms of virtue and the perfect habit. The rudimentary forms certainly can exist separate: they are a matter of temperament and inherited constitution: and the man whom nature has kindly predisposed to benevolence, she has perhaps very imperfectly prepared for prudence, fortitude, or sobriety. But one perfect habit of any one of the four cardinal virtues, acquired by repeated acts, and available at the call of reason, involves the presence, in a matured state, of the other three habits also. A man who acts irrationally upon one ground, will behave irrationally on other grounds also: or if his conduct be rational there, it will not be from regard for reason, but from impulse, temperament, or from some other motive than the proper motive of the virtue which he seems to be exercising.
Readings.—St. Thos., 1a 2æ, q. 54, art. 4; ib., q. 58, art. 5, in corp.; ib., 2a 2æ, q. 47, art. 7, 12, 13; Ar., Eth., VI., v.; ib., VI., xii., 9, 10; ib., VI., xiii., 6; St. Francis of Sales, Of the Love of God, bk. xi., c. vii.