This short note examines the text of Aquinas’ Third Way (Summa theologiae Iª, q. 2, a. 3). J. Hintikka and S. Knuuttila have argued that Aquinas’ reasoning relies on the

so-called “principle of plenitude”, as formulated by A.O. Lovejoy. A close reading of the text, however, reveals that the manuscript variants – largely ignored by the Leonine editors – are also compatible with a rejection of this principle. Such a rejection aligns more closely with Aquinas’ position in his commentary on Aristotle’s Metaphysics. On philosophical grounds, I suggest that future editions of the Summa should adopt the variant readings preserved in the Leonine critical apparatus.