Prudence is the virtue that disposes practical reason to discern our true good in every circumstance and to choose the right means of achieving it; "the prudent man looks where he is going." 65 "Keep sane and sober for your prayers." 66 Prudence is "right reason in action," writes St. Thomas Aquinas, following Aristotle. 67 It is not to be confused with timidity or fear, nor with duplicity or dissimulation. It is called auriga virtutum (the charioteer of the virtues); it guides the other virtues by setting rule and measure. It is prudence that immediately guides the judgment of conscience. the prudent man determines and directs his conduct in accordance with this judgment. With the help of this virtue we apply moral principles to particular cases without error and overcome doubts about the good to achieve and the evil to avoid.