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.

In some key areas of ethics and psychology, Seneca is at pains to distinguish his views from those of the Peripatetic followers of Aristotle. While he probably does not know Aristotle’s works at first hand, Seneca shows some knowledge of the doctrines that were favored by most Peripatetics, gleaned from secondhand discussions in such writers as Posidonius and from at least one summary account that was similar in style to Stobaean Doxography “C,” attributed to Arius Didymus. Passing references throughout his works show a consistent effort to differentiate his Stoic positions from Peripatetic views, especially on the value of externals and on the emotions. Recognition of this fact aids with the interpretation of Epistulae morales 92, which responds point for point to a list of Peripatetic doctrines. In particular, the first paragraph of that letter should be read as accommodating the Peripatetic tripartition of soul to Seneca’s Stoic commitments rather than the other way around.

Christopher Rowe argues that Aristotle in the Eudemian Ethics develops a naturalised account of Socrates’s divine sign: even people lacking in practical wisdom, Aristotle proposes, can act appropriately, and achieve a kind of happiness, because of something divine in them. But this ‘something divine’ is not (as it is for Socrates) a private inner voice, rather a kind of well-naturedness. For Aristotle, goodness is natural. The goodness of human nature explains how it is possible to do the appropriate things even without reasoning, and even do so reliably. This offers Aristotle an answer to a puzzle about our relation to the natural world. Humans, he holds, are good by nature, yet he also holds fully virtuous human beings to be relatively rare: two claims that are hard to reconcile, given Aristotle’s usual view that what occurs ‘by nature’ occurs ‘always or for the most part’. By allowing there to be a level of decency that is achievable through well-naturedness, even by those who lack full virtue, Aristotle can answer this puzzle. If this decency is achieved by many people, then there is, after all, a kind of good human development that occurs by nature and occurs regularly.