Theory of Forms
Plato's Theory of Forms provides Plato's explanation of the nature of ultimate Reality. In it, Plato upholds the distinction between ultimate Reality, what is most Real, and sensibility, the world of the five senses. In the Platonic view, the world that we experience as changing is a world of Becoming. It should not be taken, however, that the world of sense has no connection with the Forms [ιδέες].
The Forms, also understood as the Platonic Ideas reside at the top of the hierarchy of Platonic Reality and as the Forms of Being are only surpassed by the Good, a reality beyond Being. For our purpose. It is helpful to think of Being in relation to Becoming. External causes can effect changes and move sense objects but without external causes, these objects lack motion. As such, they do not exist in themselves and are not self-moving as in the case of the soul. The Forms, on the other hand, exist in themselves, needing nothing to complete themselves. Examples of Platonic Ideas or Forms are Justice, Love, Virtue and Courage. These Forms correspond, respectively, to the gods Dikē [Δίκη], Eros [Ἔρως], Virtue [ἀρετή], and Courage [ανδρεία].
For Plato, the Forms are not mere abstractions or mental constructions. Such a way of thinking belongs to a later period of Philosophy which distinguishes between inner and outer substance. In Plato, in Greek tragedy, e.g., Sophocles, and in archaic Greek life in general, truth is still an external Being that works upon human affairs. It has not yet been internalized itself to the form of rational essences in thought: in other words, pure abstractions. For Plato, the Forms are real Beings. In Phaedrus, he refers to them as personifications of the gods themselves whose reality we can recall and therefore connect with through anamnesis. In the Myth of the Charioteer of the same dialogue, Socrates explains the hierarchy of these beings and shows, in conjunction to them, the manner in which men are given, intrinsically linked, to a particular god. It appears paradoxical that Socrates both rejects and uses myth in the dialogues, his argument often relying on myth for its logos [truth].
To make sense of this, it is well to remember that every physical object can be thought to have a connection with a Form. In Platonic philosophy, this means that physical objects and discourse itself are images, copies of the fundamental reality beyond sensibility. These copies can be better or worse. They can more closely resemble the real from which they participate in ultimate reality, which Plato would not object to, or they can be bad copies. As the images of reality move further away from the reality, their participation in the forms decreases and they become mere shadows, having very little of the substance of the Forms left in them.
In Plato's conception of the participation of material reality in the Forms, it might first appear that matter and form are completely separate, therefore placing Plato further away from Aristotle's view of substance [form]. However, there is a way that it can be said that, for Plato, matter participates in the forms and derives its reality from them. Although sensible objects and the eternal Forms are distinct, objects of sense maintains a real connection to the Forms and thereby participates, through them, in Being. The closer this connection between Original and the Copy, the more reality it can be said is to be found in a thing. Because sensible objects are only images of the real, the question of discourse and of truth requires investigation of the relation of these images - and of image-making in either art or discourse or poetry - to the original from which they obtain their reality, the Forms.
In Book X of the Republic, Plato argues for a hierarchy of images using the example of the image of a bed. At the top would be that which gives the bed its essence, the Form. The highest image of the bed would be the idea of the bed that made by God. The second kind of copy [image] is an actual bed made by a carpenter. The third bed is the image of a bed made by a painter. Image-making is not reserved to the painter, however, since we learn in the Phaedrus that discourse involves a kind of image-making which can even, under certain conditions, be viewed as the highest art (262e).