 Unlike some of his contemporaries, who argued that all the virtues should be dispositions of the will (Kent 1995), Aquinas thinks that each of these four virtues perfects a different power of the soul. Bravery and temperance, indeed, are not perfections of rational powers at all. They are, however, defined in terms of right reason, and this both connects his virtue theory to the theory of natural law and helps to explain why the virtues cannot be the cause of immoral actions. The person who is “brave” in a foolhardy way would not strictly count as brave. Deepening the connection between these virtues and right reason is that Aquinas treats the intellectual virtue of prudence (prudentia, or phronēsis in Greek) as foundational to all the other cardinal virtues: “rightness and full goodness in all the other virtues comes from prudence” (Quest. on the Virtues in General 6c; see Westberg 1994). Without prudence, none of the other virtues are possible. Conversely, prudence itself requires the proper disposition of our various appetitive powers. Accordingly, Aquinas endorses the traditional doctrine of the unity of the virtues: one cannot have any of them without having all of them (ST 1a2ae 65.1).