Interpreters have long recognized that there is a problem about determining what kind of activity Aristotle thinks happiness is. Some of his remarks appear to favor a single best kind of activity, intellectual contemplation. Other evidence suggests that it is an overarching activity that has various virtuous activities, ethical and intellectual, as parts. Interpreters typically view these as incompatible theses and try to show that one or the other apparent thesis is merely apparent. The problem of determining which of two incompatible theses Aristotle believes is the Dilemmatic Problem of Happiness. But the arguments that rival interpretations amass exert pressure to think that Aristotle really is committed to both of the allegedly incompatible claims. The problem of showing how he can coherently endorse both is the Conjunctive Problem of Happiness. Any dialectically satisfactory interpretation of Aristotles theory of happiness must solve it. None has done so. It cannot be solved while laboring under the weight of three common assumptions. Chapters 2–4 argue for the falsity of those assumptions and provide materials for constructing a solution to the Conjunctive Problem.

Aristotle’s theory of human happiness explicitly depends on the claim that intellectual contemplation is peculiar to human beings, whether it is our ergon (work, function, characteristic activity) or only part of it. But there is a notorious problem: Aristotle says that divine beings also contemplate. For this reason, many interpreters affirm the Divinity Thesis: Contemplation is not proper to human beings, for divine beings engage in it, too. The Divinity Thesis thwarts solving the Conjunctive Problem. Drawing on an analysis of what divine contemplation involves according to Aristotle, I argue that he rejects the Divinity Thesis. This opens the door to an account of what is proper to humans that is able to solve the Conjunctive Problem.

I discuss Aristotle’s account of the psyche (soul) in book 1 chapter 13 of the Nicomachean Ethics, his further distinction between theoretical and practical thinking in Nicomachean Ethics VI 1, and the famous function argument of Nicomachean Ethics I 7. I also address Aristotle’s unclarity about how to characterize desire, and his skepticism about parts of the psyche in de Anima III 9. This leads to a brief discussion of Plato’s division of the psyche in Republic IV and the Phaedrus, and whether both Plato’s and Aristotle’s divisions lead to problems concerning the unity of motivation. This discussion begins to set the stage for my interpretation of Aristotelian prohairesis (often translated as “choice”), the characteristic motivation of the good person. As we shall see, the phenomenon of choice straddles different parts of the Aristotelian psyche in a way that Plato never envisaged in his own account of the psyche.