Plotinus on Primary Genera as Principles

In Ennead VI.2, Plotinus states that the genera of intelligible Being (the μέγιστα γένη of Plato’s Sophist: Motion, Rest, Being, Identity, and Difference), also labeled “primary genera” (VI.2.8.43, 8.9.1: πρῶτα γένη), “cannot be merely genera, but must also be principles of being at the same time” (2.2.10–11: οὐ μόνον γένη ταῦτα εἶναι, ἀλλὰ καὶ ἀρχὰς τοῦ ὄντος ἅμα ὑπάρχειν).1 My aim here is to unpack and explain this statement. I provide a context for its understanding in Books B, Z, and H of Aristotle’s Metaphysics and argue that Plotinus maintains that the primary genera are productive causal factors responsible for the structural constitution and articulation of the noetic world—that is, true Being—and that this view is best understood by considering Plotinus’ critical engagement with Aristotle’s account of the relationship between genus, species, differentia, and substance.