A philosophical dialogue that presents a grand cosmology in which a divine craftsman orders chaotic matter by mathematical harmony to create the cosmos as a single living being: a world-soul is woven from rational proportions, the heavens and celestial cycles are fashioned as temporal images of eternal Forms, and the physical world arises from combinations of four elements associated with regular solids; the account extends to human physiology and disease as consequences of elemental imbalance, links geometry and astronomy to the nature of perception and knowledge, and treats time as a moving image of eternity established with the creation of the heavens.