CONCEPT
Prudence
Aquinas’s name for practical wisdom—the developed capacity to perceive what a particular situation genuinely requires and to act rightly in it—the virtue no rule can contain and no optimization can replicate, and the precise human faculty that every story of AI systems gaming their metrics shows to be missing.
Prudence—Latin
prudentia—is for
Thomas Aquinas the highest of the practical virtues, and it is not caution. It is practical wisdom: the developed capacity to perceive what a particular situation actually requires and to act rightly in it. The distinction matters enormously because prudence is the bridge between a general principle and a specific case, and Aquinas was emphatic that this bridge cannot itself be reduced to a further rule. No principle, however refined, applies itself. Between the law and the deed stands judgment, and judgment is exactly what optimization is not. An AI system optimizes: it has an objective function and selects actions that maximize it. This is enormously powerful, and within a well-specified domain it can far exceed human performance. But optimization requires the objective to be specified in advance;
prudence supplies what every specification leaves out—the perception of what is unprecedented in the situation, what