The Theory of Forms

"Plato's Theory of Forms, then, seems to involve two main ideas: first, that Forms are themselves - in some way - one; and second, that Forms do not exist in the world of experience: they are 'trascendent'. As we have seen in an earlier chapter, however, Aristotle had a different view. Aristotle thought that Forms reside in the substances whose matter is organized by the Form: Forms are not transcendent but 'immanent'. The Form of a horse, for examğle, resides in each individual horse. The difference between Plato and Aristotle here is over the question of what is most fundamentally real. Does the ultimate reality of the world lie within the ordinary things of experience? Or does it transcend those things? To say that a Form of the horse is in the horse is to say that the horse is fully real in itself; the reality of an individual horse does not have to be underwritten by the horse's relationship to something outside the world."

                                                                            Tim Crane & Katalin Farkas, Metaphysics, p. 219