Editor's comment

This is Plato’s famous allegory of the cave. He maintains that the common view of things are only shadows of what is real. There exists an ideal world of ideal forms and ideas. For example, there are many forms of tables in the physical world. They display (some more than others) aspects of ideal tableness. None are perfect. But the intellect recognizes the existence of the perfect table, as well as the perfect human and the ideal of perfect beauty and goodness.

All objects and ideas in the physical world merely resemble their perfect forms. These perfect forms are eternal and only they can be the object of true knowledge. It is the soul of a person that dimly perceives and longs for this world of ideal forms.

According to Plato the universe and heavenly bodies must have the ideal form. They are eternal, perfect and unchanging. Since the sphere is the most perfect three-dimensional shape and the circle the most perfect two-dimensional one the universe must be a sphere and all motion of the heavenly bodies must be uniform circular motion.


Reading on: Plato's ideal worldview

Plato’s World of Ideal Forms and Ideas from The Republic Jowett Translation [excerpt —660 words]

Behold! human beings living in a underground den, which has a mouth open towards the light and reaching all along the den; here they have been from their childhood, and have their legs and necks chained so that they cannot move, and can only see before them, being prevented by the chains from turning round their heads. Above and behind them a fire is blazing at a distance, and between the fire and the prisoners there is a raised way; and you will see, if you look, a low wall built along the way, like the screen which marionette players have in front of them, over which they show the puppets. And do you see men passing along the wall carrying all sorts of vessels, and statues and figures of animals made of wood and stone and various materials, which appear over the wall?

They are strange prisoners… Like ourselves. They see only their own shadows, or the shadows of one another, which the fire throws on the opposite wall of the cave. And of the objects which are being carried in like manner they would only see the shadows. To them the truth would be literally nothing but the shadows of the images.

And now look again, and see what will naturally follow if the prisoners are released and disabused of their error. At first, when any of them is liberated and compelled suddenly to stand up and turn his neck round and walk and look towards the light, he will suffer sharp pains; the glare will distress him, and he will be unable to see the realities of which in his former state he had seen the shadows; and then conceive some one saying to him, that what he saw before was an illusion, but that now, when he is approaching nearer to being and his eye is turned towards more real existence, he has a clearer vision… will he not be perplexed?…

He will require to grow accustomed to the sight of the upper world… The prison-house is the world of sight, the light of the fire is the sun, and you will not misapprehend me if you interpret the journey upwards to be the ascent of the soul into the intellectual world according to my poor belief, -- whether rightly or wrongly God knows. But, whether true or false, my opinion is that in the world of knowledge the idea of good appears last of all, and is seen only with an effort… [and] just as the eye was unable to turn from darkness to light without the whole body, so too the instrument of knowledge can only by the movement of the whole soul be turned from the world of becoming into that of being … [and] you have seen the beautiful and just and good in their truth.