I develop the relatively familiar idea of a variety of forms of knowledge-not just propositional knowledge but also knowledge-how and experiential knowledge-and show how this variety can be used to make interesting sense of Plato's and Aristotle's philosophy, and in particular their ethics. I then add to this threefold analysis of knowledge a less familiar fourth variety, objectual knowledge, and suggest that this is also interesting and important in the understanding of Plato and Aristotle.