But slowly his pupils will adjust to his new environment, and for the first time in his life, he will perceive real objects – at first only those within his reach. This perception will open the eyes of his mind to a terrible and for him revolutionary truth: up to now, he has confused shadows with reality. A Copernican revolution takes place in his life! To become aware that he has lived in error since his very youth is an earth-shaking discovery. But by now our hero's pupils are capable of looking upwards, and the last thing which he will be able to behold – because of its luminous brightness – is the sun, the source of all light. Plato points to the fact that the more sublime a thing is, the more difficult will it be for weak-sighted human beings to perceive it, even though it is most real and luminous, being the very source of everything else, just as the sun is the source of light.
The philosopher can now draw the conclusion that man can be blinded both by darkness, (because of lack of light), and by light when the very luminosity of an object is too strong for his weak eye sight to contemplate.
He now recalls the sad fate of his fellow prisoners, and instead of enjoying the beauty which he has perceived, he decides to go back to the cave, and inform them of their error. Plato here clearly hints at the fact that truth is "ours" and should not remain the "property" of a single individual who has been blessed with discovering it.
Out of loving concern for the welfare of the unfortunate prisoners, the philosopher decides to re-enter his place of birth. But upon doing so, he finds himself plunged into darkness. Once again, his sight fails him, but this time, for the opposite reason: there is too little light. Nevertheless, gropingly he finds his way back to his old place.
The prisoners – as usual – kill time trying to identify the shadows appearing on the wall; the first one who succeeds is, of course, the smartest. The philosopher who used to be good at the game, is now totally helpless; having seen real objects, shadows strike him as so unsubstantial that he can no longer victoriously compete with his companions. As a result, the latter come to the conclusion that anyone who leaves the café should be punished by death, for by so doing, he comes back without his eyes. (An obvious reference to the fate that Socrates suffered because he tried to make men "see"). It is worth noticing that the prisoners show no interest whatever in questioning the philosopher. They are so used to their conventions, their prejudices and their petty concerns, that they have no longing whatever to transcend the narrowness of their views. They are used to their dark cave and feel comfortable in it. (Kierkegaard expressed the same truth by pointing out that many men actually choose to live in the cellar of their house.)
We are back to our pet theme: blindness can be caused by an excess of light, or by a defect of light. But in both cases, the result is identical – we cannot see.