In the Timaeus, the most metaphysical of Plato’s writings and the one most influenced by Pythagoras, Plato returned to a consideration of science and the natural world; two subjects which Socrates had abandoned long ago. It is not like most of his other writings. Socrates is present, but he plays only a minor role. The book is not really a ‘dialogue’, aside from a brief introductory conversation. It is mostly a monologue, in which the character named Timaeus weaves an all-encompassing myth of creation.
Plato warns us that his myths and parables are not to be taken literally. This, however, is not equivalent to saying that they should not be taken seriously. On the contrary, they are symbolic illustrations of what for Plato is most true and important, and he uses them at the uppermost reaches of his thought, where our common expository language fails.
Like Thales, Plato here is asking the fundamental scientific question, “What is the essential nature of reality?” Like Pythagoras and contemporary physicists, the answer he gives is mathematical rather than material. The book is a difficult and startling document, which attempts to explain everything from the meaning and purpose of creation, to the structure of matter, the wonders of nature, the plan of the heavens, and even the principles of medicine, physiology, and psychology. It has been of unprecedented importance in the history of western thought.
You can find out more about the Timaeus in my book LOVE, WISDOM, AND GOD: The Longing of the Western Soul. I discuss it at great length.