Certainty of Prudence

Necessity of Certitude.—Prudence, being an intellectual virtue, must have certainty (see on the Certain Conscience, 640 sqq.). But with regard to particular contingencies (e.g., whether Balbus ought to marry Caia) there are various kinds of certainty.

(a) There is the certainty of knowledge based on a generalization from experience of what happens in the majority of cases (e.g., that persons well mated by reason of birth, age, dispositions, etc., marry successfully). This kind of certainty belongs to moral science.

(b) There is also a certainty of knowledge based on the indications in a particular case (e.g., that Balbus and Caia appear to have congenial dispositions and a mutual affection that will make their marriage a success). This is the certainty of opinion, and while it may suffice as a rule for conscience (see the Systems of Conscience, 672 sqq.), events do not always verify its predictions. Hence it is said: “The thoughts of mortal men are fearful and our counsels uncertain” (Wis., ix. 14).

(c) There is finally the certainty of practical truth, which consists in harmony with a good will. This is the certainty that is proper to prudence, for this virtue is not a matter of reason alone. Hence, even though a matter properly decided on should not take place or should fail of the purpose intended (e.g., if the marriage of Balbus and Caia is prevented or turns out badly), it remains that prudence was not deceived in its decision, for that decision when made was according to right reason and a good will (see 578).