This presentation will discuss the folklore motif known as the rule of three. It is an attempt to account for some instances of this trope as a metonymic process that is manifest in the way that referents acquire words to refer to them, the way that philosophers theorize that proper names are learned, and the way that mythological problems are solved, with examples from Hesiodic and Homeric epic. It also will discuss the apparent fact that in ancient Greece as in ancient India and perhaps elsewhere, a large and diverse epic tradition seems to have been systematized into a pair of epics, the Iliad and the Odyssey or the Mahābhārata and the Rāmāyaṇa, that function in contrast to one another, without a third instance. Finally, it will discuss the notion of the tertium comparationis and its conceptual significance for the study of epic traditions that are historically related as well as those that are unrelated to each other but that so often seem to create new understanding when they are placed side-by-side.