 Next, Aristotle turns to his own account of happiness, the summit of Book I. The account depends on an analogy with the notion of function or characteristic activity or work (ergon). A flutist has a function or work, i.e., playing the flute. The key idea for Aristotle is that the good of flute players (as such) is found in their functioning as a flutist. By analogy, if there is a human function, the good for a human is found in this function (1097b20–30). Aristotle then turns to the human soul. He argues that, in fact, there is a human function, to be found in the human soul’s characteristic activity, i.e., the exercise of reason (1098a1–20). Then, without explanation, he makes the claim that this rational function is expressed in two distinct ways: by deliberating and issuing commands, on the one hand, and by obeying such commands, on the other. The part that has reason in itself deliberates about decisions, both for the short term and the long. The part that obeys reason is that aspect of the soul, such as the appetites, that functions in a human being under the influence of reason. The appetites can fail to obey reason; but they at least have the capacity to obey (as, for example, such autonomic functions as nutritive and metabolic ones do not).