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 has the resources to solve the Conjunctive Problem of Happiness and thus to vouchsafe the necessity of ethically virtuous activity while clarifying the kind of priority that contemplation has. Among these resources is his theory of predication as articulated in the Organon, his toolkit for all sorts of philosophical inquiry. This theory allows us to understand the coherence of what have appeared to many to be fundamentally discrepant answers to the question about what kind of activity happiness is.

The first commonly held thesis that prevents solving the Conjunctive Problem is the Divergence Thesis, according to which Aristotle thinks that it is possible to possess theoretical wisdom and reliably manifest it in contemplation without possessing practical wisdom and reliably manifesting it in ethically virtuous activities. This thesis, though widely endorsed on the basis of a single passage, is false. The apparent support provided by that passage fades away on closer inspection. Once freed from the restrictive grip of the usual interpretation, we are prepared to understand Aristotles distinctive account of the motivations of intellectually virtuous agents. His account invites us to revisit assumptions about what the ideal epistemic agent looks like that have figured prominently in recent experimental philosophy.

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.

It is standardly believed that Aristotle thinks that there are two kinds of happiness, one corresponding to intellectual contemplation and the other corresponding to ethically virtuous activities, and the former kind is superior to the latter. This is the Duality Thesis. It is notoriously problematic and does not follow from anything that Aristotle has said to that point. It also prevents solving the Conjunctive Problem of Happiness. Interpreters have felt forced to affirm the Duality Thesis by its apparent textual inescapability. However, the apparent claim depends on supplying “happy” or “happiest” from the previous sentence, as is standard among translators and interpreters. I argue for an alternative supplement that commits Aristotle to a much less problematic and unexpected position.

Reece discusses Diogenes of Apollonia’s claim that “all existing things are differentiated from the same thing and are the same thing” (DK 64B2, Simp. Phys. 151.31–32), namely air. He examines Diogenes’ principle that causal interaction and change require some sort of uniformity among the relata, and considers the questions which this principle raises.