This paper shows that our principal ancient source for the metaphysical views of the second-century Platonist Harpocration of Argos drew on his interpretation of Plato's Cratylus. This is important because there is no other evidence of the Cratylus being read for its metaphysical content until Proclus, 300 years later. It also changes our understanding of Harpocration: he is generally supposed to share the metaphysical views of Numenius, but his exegesis of the Cratylus reveals him to be a faithful student of Atticus.