 The theoretical aspect is also expressed as articulate reasoning about the goal. In Plato’s view, the ability to explain why he does what he does is one of the most important characteristics of the craftsman. In the Charmides, Socrates says that we test the physician by questioning him since he understands health (Charm. 170e5–7). Expanding on the idea of testing, Socrates says they will investigate the physician in what he says and in what he does, on whether what he says is true and whether what he does is right (171b7–9). This theoretical side of craft is further developed in the Gorgias. In his conversation with Polus and later in his conversation with Callicles, Socrates carries on a sustained reflection about craft. In his conversation with Polus, Socrates distinguishes four crafts (technai: medicine, physical training, judging, and legislating; the first pair are concerned with the body and the latter with the soul (464b). These crafts provide their care always for the best, either of the body or of the soul (464c). Unlike empiric practice (empeiria), technê has an account to give by which it provides the things it provides, an account of what their nature is, so that it can say the cause of each (465a). In the conversation with Callicles, Socrates returns to this account, when he seems especially interested in the ability of technê to give an account. He says medical technê investigates the nature of the thing it cares for (therapeuei) and the cause of what it does and has an account to give of each of them (501a). In the first instance, medicine cares for, or treats, the body; but, more particularly, it cares for the good of the body, i.e., its health. So, this technê has an account to give of health and of what it does to achieve the end of health.