 As for rulership, John argues that the pope cannot be the supreme temporal ruler because the spiritual and temporal powers should be held by different persons. John gives the traditional reasons (see  §6),  emphasizing the argument that the priest should be exclusively devoted to spiritual affairs (117–8). The temporal power is not established by, or in any way caused by, the spiritual power. Both come from God, but neither comes through the other. The spiritual is in some sense superior, but not as being the cause of the temporal power (93, 192). The basis of the distinction between the two powers is not subject matter or ends, but means. Each power is limited to its own appropriate means of action; the secular power uses natural means, the Church uses supernatural means (142–61). This is very much like Thomas Aquinas’s picture of two powers leading mankind toward the goals of human life in ordered hierarchy, one using natural means and the other supernatural. Thomas infers from the fact that the Church is concerned with the highest end the conclusion that the pope ought to direct the secular ruler (see above,  §9.1).  John explicitly rejects this line of argument. Teaching is a spiritual function, but in a household the teacher does not direct the physician. The physician exercises a higher art than the pharmacist, but, though the physician guides the pharmacist, he cannot give authoritative directions or dismiss the pharmacist. Such officials in a great household do not direct one another, but are all under the direction of the head of the family. Similarly both pope and prince derive their authority from God, who sets the limits of their power, and he has not subordinated one to the other (182, 184–93).