The significance of this project ought to be evident. First, it shows that Plato’s Forms simply are essences, not things that have an essence and that Plato’s theory of Forms is just that, a theory of essence. Secondly, it shows that, if we have reason to raise and take seriously the ti esti (‘What is it?’) question, then we have reason to take seriously Plato’s theory of essence, the theory of Forms, with the remarkable characteristics that Plato attributes to essences and Forms. thirdly, it presents a challenge to those philosophers today who think that essentialism is an optional item on the philosophical menu. Finally, it presents a challenge to the tendency, typical to the essentialists of today, to think that the only option is Aristotelian essentialism, and that Platonic essentialism, if it can be made out at all, is simply Aristotelian essentialism with the addition of certain Platonic commitments that are both unattractive and optional. The projects demonstrate that Plato’s essentialism is a well-argued, rigorous and coherent theory, and a viable competitor to Aristotle’s essentialism.