Question XI: On the precepts of prudence

It is not doubtful that the Virtue of Prudence, which is the rule of all the virtues, is a matter of precept; for all the other affirmative precepts about the acts of the virtues presuppose the affirmative precepts of prudence, both in general and in species, by this very fact, that they must be done prudently from right election through prudence. Similarly all the negative precepts, forbidding the contrary acts of the vices, presuppose the negative precepts of prudence, inhibiting the acts of imprudence by which vicious acts would be badly directed.

AND hence is had the reason why precepts of prudence had not to be given in the Decalogue: for these stand antecedently to all the precepts of the Decalogue.

BUT these precepts of Prudence are set forth in many places, Leuit. 19. Thou shalt not do Calumny to thy neighbor, namely through craftiness, deceit, or fraud. Deuter. 25. Thou shalt not have in thy sack divers weights, a greater and a less. Prouerb. 3. Lean not upon thy own prudence; that is, be not, assuredly, tenacious of thine own judgment.

Prouerb. 4. Acquire prudence, and seize it, and cap. 9. Walk by the ways of prudence. And Matth. 10. Be ye therefore prudent as serpents, and simple as doves, where St. Jerome says: That by prudence they may avoid snares; by simplicity not do evil. And the craftiness of the serpent is put as an example, because with its whole body it hides its head, that it may protect that in which life is. So let us guard with the peril of our whole body our head, who is CHRIST, that is, the faith whole and incorrupt. This is the interpretation also of Hilary, can. 10. in Matth. Epiph. haeresi 37. and St. Bonaventure everywhere, as I said disp. hac quaest. 2. where I also brought forward other properties of the serpent, of which some also bring forward Rabanus, Remigius, and many others.

TO the precept of prudence also pertain those words Rom. 12. Be not prudent in your own selves according to Prouerb. 3. Lean not upon thy own prudence. Be not wise in thine own conceit. And cap. 4. Possess prudence. And below: Let thine eyes see things that are right, and let thy eyelids go before thy steps. Direct the path for thy feet, and thy actions shall be established. Tit. 2. Let them be sober, chaste, prudent, etc. first Peter 4. Be prudent therefore, and watch in prayers. Matth. 10. Be ye therefore prudent as serpents.

There are also negative precepts of abstaining from the things opposed to Prudence, related above.