In the Timaeus, Plato has the eponymous character narrate a kind of creation myth which explains the construction of the universe by an intelligent agent. Interestingly, the account that Timaeus gives actually arises in the context of a discussion about the social structures and activities of the ideal state. In the dialogue’s opening scene, Socrates quickly lists the characteristics that he and his three friends (Critias, Hermogenes, and Timaeus) had agreed upon during the course of the previous day’s discussion—all of these characteristics being reminiscent of those mentioned in Books III through V of the Republic—and then challenges his friends to turn this ideal account into a description of this state’s international policies, should it ever become a reality. Critias responds by telling a story that his great-grandfather reportedly heard from the great Athenian lawmaker Solon. While traveling in Egypt, Solon was told that primeval Athens, a city lost to Greek history but known by the Egyptians, was the noblest state on earth and led Europe in its efforts to repel an invasion by the empire of Atlantis. From there, the trio decides to give an exhaustive account of forgotten Athens, an account which begins with Timaeus, an astronomer-philosopher, describing the creation of the universe and the resulting implications for human nature. Timaeus’ cosmological story depicts the universe and all it contains as a harmonious and rationally ordered system that is properly regarded as good. In fact, Timaeus attributes both a soul and godhood to the universe (34B).
The central point of relevance regarding the beginning of the Timaeus is that it starts with issues of ethics and politics and then undergoes a secondary shift to a detailed cosmological-physical description, provided only so that Critias, Hermocrates, and Timaeus can respond to Socrates as fully as possible. Therefore, although the Timaeus is chiefly about the manner in which a divine craftsman called the Demiurge fashioned the universe, its primary significance is ethical rather than metaphysical or scientific. Considering the Timaeus to be the first of a projected trilogy of dialogues that was never completed by Plato (Timaeus, Critias, Hermocrates), the early 20th century classical scholar Frances M. Cornford writes that “[t]he whole cosmology of the Timaeus is only a preface to the legendary picture of the ideal state in action [as featured in the Critias] and to whatever were to have been the contents of the Hermocrates." Furthermore, the Timaeus is an extension or extrapolation of “the structural analogy between the state and the individual soul” which Plato laid out in the Republic and so “the chief purpose of the cosmological introduction is to link the morality externalised in the ideal society to the whole organisation of the world." This means that the Timaeus is a continuation of the Socratic-Platonic tradition’s focus on the “examined life” and questions of the good, rather than solely a competitive response to the proto-scientific, object-oriented metaphysics of the pre-Socratics. Plato’s interest is not so much in how the Demiurge uses the Forms in order to give shape and intelligibility to the universe as it is in what this means for human conduct and ethical/political relations.
None of this is to say that the Timaeus has no relationship to ancient Greek cosmology. In his commentary, Cornford explains how Plato, operating through the character of Timaeus, rejects the various cosmologies advanced by earlier schools of Greek philosophy, especially the Pythagoreans and the Atomists. Whereas the Pythagoreans saw the universe as developing in a kind of vegetative process in which it drew nourishment from a kind of primitive, unshaped matter surrounding it, the Atomists believed that the universe had arisen from the pure blind luck of lifeless particles colliding. Considered from the perspective of early Greek philosophical cosmology, Plato’s contribution was to offer the first account of a universe created according to intelligent purpose, with the result that the universe was regarded as capable of being understood, lived in, and shaped according to human reason. Platonic philosophy posited a basic congruity between the objects of human thought and the nature of ultimate reality, a congruity which was also ethical insofar as human reason was capable of structuring human behavior according to the divine order. This stood in stark contrast with earlier tendencies within both philosophy and Greek culture at large, which saw the Olympian gods as jealously hoarding their knowledge and powers. Instead of fickle deities and the harsh world in which the Trojan War was fought and the Persians repelled, Plato gives a description of a kind of craftsman deity who is good and “[d]esiring then, that all things should be good and, so far as might be, nothing imperfect […] took over all that is visible […] and brought it from disorder into order” (30A). The creator is motivated by his own goodness and implants this goodness into the fabric of the created order. However, he is not omnipotent and so his work is constrained by the limits of his materials, namely matter and whatever else is provided to him by Necessity.
But despite this cosmological significance, the main impetus behind the Timaeus is how it serves to connect the order inherent within the universe with human goodness, a linkage in which the good takes precedence and is more immediate. Indeed, as Timaeus explains, the universe is ordered because it is good and an account of the details of that organization can only be probable, whereas its essential goodness is taken to be known (29A-29C).