Scholastic philosophers can be quite funny. What's more, they have good reason to be: Aristotle himself lists ready wit (eutrapelia) among the virtues, as a mean between excessive humor and its defect. Here, I assess Scholastic discussions of humor in theory, before turning to examples of it in practice. The last and finest of these is a joke, hitherto unacknowledged, which Aquinas makes in his famous Five Ways. Along the way, we'll see (i) that the history of philosophy is not so hostile to humor as is commonly supposed; and (ii) that the competing theories of humor like the Incongruity Theory and the Release Theory are not altogether incompatible. We'll also see at least one example of an apparent attempt by modern translators to excise humor from a medieval text. Our considerations will open a window into what oral discussion and debate at medieval universities was actually like, and how we should understand the relationship between the texts we have now and the exchanges that actually occurred then.