c) The Fundamental Accomplishment of the Idea: Letting-through the Being of Beings

Our guiding question is: what is the connection between idea and light? Why are the ideas depicted through brightness? We have attempted to clarify both the essence of idea and the essence of light. What are the consequences for establishing the connection between the two?

What emerged as the essence of light and brightness, namely letting-through for seeing, is precisely the basic accomplishment of the idea. The essence of light is letting-through for sight. If light, as in the allegory, is meant in a transferred sense (likewise transparency, of brightness and sheet of glass), seeing must correspondingly be meant in a transferred sense (in the usual sense of seeing the book): the seeing of beings (book, house, chair). What is seen in and as the idea is, outside the allegory, the being (the what-being and how-being) of beings. Ἰδέα is what is sighted in advance, what gets perceived in advance and lets beings through as the interpretation of 'being'. The idea allows us to see a being as what it is, lets the being come to us so to speak. We see first of all from being, through the understanding of what a particular thing is. Through its what-being the being shows itself as this and this. Only where being, the what-being of things, is understood, is there a letting-through of beings. Being, the idea, is what lets-through: the light. What the idea accomplishes is given in the fundamental nature of light.

So the connection between light and the idea is clear. We see a being as a book only when we understand its sense of being in the light of its what-being, of the Idea'. We start to understand why from the beginning of the allegory the comportment of man towards beings is bound up with light and fire. Thus we also say 'it dawns on me' [mir geht ein Licht auf]; we do not mean that for the first time we become aware of something, but that we now genuinely know what we have all along known, namely what something is.

But this does not explain why precisely light and seeing (ἰδέα) are taken up in relation to the understanding of being. Perhaps this has something to do with the avoiding of ἀλήθεια.

If there were no light at all in the cave, the prisoners would not even see shadows. But they do not know anything about the light which is already in their sight, just as little as someone who sees a book knows that he already sees something more than, and different from, what he can sense with his eyes, i.e. that he must already understand what 'book' as such means.