My title is tentative, I know, and so is what follows. But we always must begin with the tentative, in its etymological sense of stretching — stretching toward what we don’t yet fully know and yet which grips us by means of anticipations present in the desire to know. I want to write a straightforward statement of what I believe forms to be in Plato. I have no book in front of me and so will not cite any texts. My purpose is to lay bare my own pre-understanding so that I will have a sample to test against the texts themselves. The dialogues are the testing-stone, the basansos, that I can measure myself against when I do return to them, and measure myself without evasions. (It is as if I write what follows in answer to a kind of subpoena from a divine judge — I will really try not to perjure myself!) My four main inspirations are clearly Plato, Aristotle, Plotinus and Bernard Lonergan, and I will be interested in future study to tease out the degree to which the latter three influences may have caused me to deviate from Plato’s root sense. (I don’t necessarily mean “deviate” in a bad way — a deviation may be an improvement.) So what follows is an attempt to articulate (in eight propositions) my still-meager understanding of what Plato may mean by eidos/form:
1. Form/eidos is a form of possibility. Actualities may con-form with particular possibilities, but it is the possibility and not the actuality that constitutes the form.
2. Eidos is derived from a verb that seems “to see.” This seeing means something closer to recognition, in the way that we may say “I see what you mean” when we understand something. What we understand is this case is form. Insight is the actualization of formal recognition.
3. Possibilities “govern” the world of actuality in two ways: (i) as limiting what can be actual; (ii) as desirable possibilities that motivate actualities into being. The first sense is form as “possibility”; the second is form as “potency.”
4. Possibilities are not located in space and time, although their actualizations are. An evil tyrant can destroy every book on the planet and yet the possibility of a book abides. Forms are therefore eternal and “exist” independently of the actual world. They are “separate” from the world of things in this sense and this sense only. There are possibilities that do/have not become actualities, but there are no actualities that are not expressions of possibility.
5. A form/eidos is what would be known about something-in-some-way if we knew it. A form is both the objective of knowledge and the heuristic anticipation that guides that knowing. The form is already potent in the attempt to know and becomes actualized in full knowing.
6. Since form is eternal and since all thinking is being guided by form, thinkers already potentially know all things. This is different from actually knowing them.
7. Form becomes potency when it corresponds to some good of the actual. The good, which is “beyond being,” is not a form itself and so it is impossible to have an actual knowledge of it. The good is transcendent to every desire to comprehend it, but it is always present in any desire as the light and fire that drive it.
8. I understand “the form of the good” to be different from “the good itself.” The form of the good is fully potent when the good itself is an object of study, but since the good cannot be reduced to form, the good is always an object transcendent to its study.
shared ignorance 
My immediate reaction is that your position is solid and probably true except that I always learned (wrongly perhaps) that the forms for Plato were what was more real than the sensible world. Is this whole area of traditional interpretation of Plato really a misinterpretation or are you saying that on this point Plato has to be improved. When you understand the forms to be possibility that can be potency, are you saying that possibility precedes actuality?
Jay,
(1) I think the forms are “more real” for Plato — more real in the sense that actualities must “realize” possibilities and that until a possibility is fully actualized, the actuality is only deficiently “real” with respect to that possible form.
(2) I think a lot of the conventional (dismissive) interpretation of Plato is just wrong. Chief among the misunderstandings is to assume that the form-hypothesis is a *doctrine* of some kind and a straightforward metaphysical account of how things are. I think he conceives it as a hypothetical thought experiment (see the Parmenides dialogue) that is particularly productive of noetic insight, an insight that cannot be directly verbalized. One source of the dismissal is the critique of Aristotle, but I’m not sure that Aristotle was critiquing Plato himself as much as bad doctrinal versions of his thought. In fact, the stiffest objections against “Platonism” (including the “Third Man argument”) are in Plato’s dialogue, Parmenides! Plato was aware of the points where the hypothesis breaks down.
(3) Yes, I think Plato’s hypothesis implies that possibility precedes actuality, since possibilities are eternal and actualities have shelf-lives. Aristotle’s innovation was to reverse the priority and make the reality of active ousia prior. To do this he had to conceive of an eternal actuality that is is neither generated nor corrupted in which all forms are already actualized — see the discussion of the unmoved mover in Physics or the idea of Active Mind in De Anima. What I don’t know is whether Aristotle is innovating or expanding upon Plato’s unwritten doctrine. There are Aristotelian elements in dialogues like Sophist, Timaeus and Parmenides — I like to think that Plato and Aristotle were learning from each other!
By the way, if Aristotle’s conception of the priority of substance to form *is* a novelty and a departure from Plato, I think I lean more in Aristotle’s direction. I am not sure that they are opposed doctrines as much as differences of emphasis within the same philosophical vision.
wow!!! Wonderful introduction. Very helpful. Your site is a way for me to “Employ your time in improving yourself by other men’s writings, so that you shall gain easily what others have labored hard for.” If I were to read Plato just by my self I would not have the benefit of ages of thought on the material. So much of its interpretation and implications that I would miss out on. Im completely fascinated by these concepts and assert my self that truth and real reality are not approachable but instead what are senses or higher reasoning skills can uncover are only parts of a whole. Im anxious to learn to what degree of certainty I can believe this? And what mechanisms I can use to improve or degrade the degree?
Epistemologist — Thanks for the compliment but keep this in mind — I’m not sure what I wrote is true! I just pray it is more helpful than harmful. As for your question, the important step in moving toward knowledge of form is to understand the problematic of opinion, through which we must all trudge. I should have something up tomorrow on that.
ha! I see what you’re doing here…at the outset.