 A significant refinement of this technê is found in Cicero’s On Ends. In Book V, Piso, representing the views of Antiochus of Ascalon, gives an overview of philosophical schools. The account depends on the notion of the highest good (summum bonum) because differences about the highest good define the possible schools. The explication of these differences begins with an analogy drawn from the crafts (artes, Cicero’s Latin for the Greek technai). First of all, the art is different from its object. Second, as medicine is the art of health and navigation the art of guiding ships, so prudence (practical wisdom) is the art of how to live (vivendi ars est prudentia). Piso presents this last claim as common to all the schools, or at least as a good way to present an element which is common. Next he says that whatever prudence would aim for is something suited to our nature and the object of natural impulse (what the Greeks call hormê). Stoics hold that prudence aims for the primary objects of nature. The primary objects of nature include such things as life and health. However, Stoics do not hold that actually obtaining the primary objects of nature is the highest good. Rather they maintain that making every effort to obtain them (i.e., appropriate ones among them, given the circumstances), even if one is unsuccessful, is morality and is the only thing desirable for itself and the highest good (V.16–20).