 Aquinas’s worldview is thoroughly teleological, inasmuch as he holds “it is necessary that all agents act for the sake of an end” (ST 1a2ae 1.2c). There is a distinction to be drawn, however, between those agents that are unable to understand their end and rational agents, who “move themselves to their end because they have control over their acts through free choice” (ibid.). It is for rational agents that ethical questions arise. Aquinas follows Aristotle in supposing that human choices must be ordered toward a single ultimate end: “there must be some ultimate end on account of which all other things are desired, whereas this end itself is not desired on account of anything else” (Comm. Nic. Ethics I.1.22). This ultimate end, whatever it is, can be referred to as happiness (beatitudo). In the Treatise on Happiness from the start of ST 1a2ae, after working through various predictably unsatisfactory candidates for our ultimate end—not riches, not honor, not pleasure, and so on—Aquinas arrives at the view that happiness consists primarily in intellectual contemplation. And since the highest truth and the greatest good are of course God, our ultimate happiness must lie there: “final and complete happiness can consist in nothing other than the vision of the divine essence” (ST 1a2ae 3.8c). Human beings possess this most fully in the life to come (Brown 2021), but even in this life Aquinas’s conception of happiness is strongly intellectualist: “it is clear that people who give themselves to the contemplation of truth are the happiest a person in this life can be” (Comm. Nic. Ethics X.12.2110).