Properties of the Universe
Plato's Atlantis described in Timaeus and CritiasTimaeus describes the substance as a lack of homogeneity or balance, in which the four elements (earth, air, fire and water) were shapeless, mixed and in constant motion. Considering that order is favourable over disorder, the essential act of the creator was to bring order and clarity to this substance. Therefore, all the properties of the world are to be explained by the demiurge's choice of what is fair and good; or, the idea of a dichotomy between good and evil.
First of all, the world is a living creature. Since the unintelligent creatures are in their appearance less fair than intelligent creatures, and since intelligence needs to be settled in a soul, the demiurge "put intelligence in soul, and soul in body" in order to make a living and intelligent whole. "Wherefore, using the language of probability, we may say that the world became a living creature truly endowed with soul and intelligence by the providence of God" (30a-b).
Then, since the part is imperfect compared to the whole, the world had to be one and only. Therefore, the demiurge did not create several worlds, but a single unique world (31b).
The creator decided also to make the perceptible body of the universe by four elements, in order to render it proportioned. Indeed, in addition to fire and earth, which make bodies visible and solid, a third element was required as a mean: "two things cannot be rightly put together without a third; there must be some bond of union between them". Moreover, since the world is not a surface but a solid, a fourth mean was needed to reach harmony: therefore, the creator placed water and air between fire and earth. "And for these reasons, and out of such elements which are in number four, the body of the world was created, and it was harmonised by proportion" (31-33).
As for the figure, the demiurge created the world in the geometric form of a globe. Indeed, the round figure is the most perfect one, because it comprehends or averages all the other figures and it is the most omnimorphic of all figures: "he [the demiurge] considered that the like is infinitely fairer than the unlike" (33b).
The creator assigned then to the world a rotatory or circular movement, which is the "most appropriate to mind and intelligence" on account of its being the most uniform (34a).
Finally, he created the soul of the world, placed that soul in the center of the world's body and diffused it in every direction. Having thus been created as a perfect, self-sufficient and intelligent being, the world is a god (34b).