Perhaps the most famous legacy of ancient Greek thought is Plato’s Theory of Forms. Pretty well everyone has heard of it, and, even if they aren’t much interested in philosophy, they have some notion of what the theory is about. It was a stunningly innovative idea, a grand theory, and one with which Plato wanted to do a lot of philosophical work, and wanted to explain many things that seemed mysterious. And, of course, right from the get-go, there were lots of voices that were highly critical of the theory. Over the centuries, most of the criticism of Plato’s theory (and its later versions) has borne on the question whether such things as Forms can really exist: these ideal entities that are, on the one hand, non-material, but, on the other, not just ideas in people’s individual heads. Could such strange things possibly exist? In this talk I want to explore a new tack of criticism. The gist of it is that Plato, without realizing it, really had two quite different understandings of the Forms at work in his thought. On the one hand, he pictured Forms as absolutely marvellous entities, the supremely perfect exemplars of whatever was in question. Thus the Form of Bed would be the most perfect, the most splendid, of all possible beds. We can call this picture the “Archetype” of Bed. But on the other hand he also thought of Forms as something much leaner, basically, the necessary and sufficient conditions of Bed—a platform for lying on. This picture we can call the “Essence” of Bed. My argument is that Plato never really saw the difference between Archetypes and Essences; he wobbled between pursuing the one and the other. And this ambiguity dramatically weakens his theory.