The basic aim of the Timaeus. The Timaeus is an account of the creation of the natural world -- and the natural world includes us. That is, it is a cosmogony. Cosmogonies can be mythic/ religious (e.g. Genesis 1) or rational/ scientific (e.g. the Big Bang). (Question: Which is Plato's?)
A puzzle about Plato's motivations. As we discussed last class, Plato thinks the material world we see and touch is NOT the fundamentally real world. Rather, Plato thinks the true world is the world of the Forms, which are apprehended only through reason or intelligence. So why would Plato write the Timaeus, since it is an account of how the material, perceptible world came into being?
Plato admits that no claims about (the origin of) the perceptible world are absolutely certain knowledge; this is because there is absolutely certain knowledge only of the Forms. Plato explicitly says that the Timaeus is only a "likely story," but it is "no less likely than any other" (29c). Given that our subject matter is the changing, material, perceptual world, the account given in the Timaeus is the best we can do -- no matter how much evidence we assemble, and no matter what experiments we conduct.
The answer. This leads us back to the earlier question: Why does Plato bother doing cosmology (or any other sort of natural science)? The short answer: the universe is the product of a supremely intelligent and beneficent goal-directed agent, who used the Forms as models to create the world. Put otherwise, Plato wants to "reveal the operations of reason in the universe" (GER Lloyd, 72).
Plato gives us two versions of his cosmological story:
The eternal creator (the "demiurge" or master craftsman) wanted to make the world like himself, because he is good and wants the world to be good like him. Thus, he changes "disorder into order" (30a) -- we find something like this transition in many mythical accounts of creation. He made this world (30c) "a living creature with soul and reason" in "which all other living creatures are parts." The creator made the world out of earth, air, fire, and water. This world is shaped like a sphere (which the Greeks considered the most perfect shape), it rotates (this explains the stars' nightly revolution), and it is self-sufficient. Plato concludes that the world is "a blessed god" (34b).
Time, according to Plato, did not exist before the Demiurge created the universe. Specifically, time is "brought into being" (38c) by the regular orbits of the sun, moon, and the 5 planets that Greeks of Plato's time knew about. For example, a month is the moon completing one orbit around the earth, and a year is the sun completing one orbit around the earth. We also see here that Plato has relatively good astronomical information: he knows, for example, that Venus and (to a greater extent) never appear far from the sun's location on the horizon (38d). He appears also to know about retrograde motion of planets -- a phenomenon that will be very important when we start studying Copernicus and the Scientific Revolution.
Humans, according to Plato, were created by the children of the Demiurge, and this explains our dual nature. Because we are not directly descended from the Demiurge, we are not gods ourselves, but there is nonetheless something "divine" and "immortal" in us (41c): our rational souls, which are god-like. So humans lie between two realms: the ever-changing material realm grasped via sensation, and the eternal, unchanging realm of the Forms, grasped via reason. Because we have one foot in the material realm, says Plato, we have desires for material pleasures: we are subject to appetites for food, money, power, and sex -- and we are subject to anger, to envy, and to other emotions that cloud our rational judgement (42a-b). But because we have the other foot in the immortal, divine realm, we can understand the eternal and unchanging truths of mathematics, and study and understand the concepts of justice and goodness. Lastly, note (44d) that Plato says our heads are round because the gods were copying the shape of the universe -- the sphere is the most perfect shape, and since the head rules the rest of the body, it should have the best shape and the best motion (rotation, as opposed to back-and-forth, up and down).
There are two kinds of cause, according to Plato (46e):
1. "causation that belongs to the intelligent nature": the realization of a purpose or goal
2. "things that are moved by others, and set yet others into motion": action by contact/ transfer of motion = "causation by necessity"
Examples. Type 1: The cause of my knife's being sharp is that someone designed it for cutting things. Type 2: The immediate cause of the baseball leaving the stadium is that a bat hit it very hard in that direction.
Why do we have a second version of the creation story? Because "the generation of this universe was a mixed result of the combination of necessity and reason" (48a), and the first version does not take the second kind of cause (causation by necessity) into account. Plato tells us, though, that reason "overruled necessity" when creating the universe, and there was a "victory of reason."
We need to add in the receptacle to the creation story, plus the Demiurge and the Forms. What is the receptacle? Fire, earth, air and water are not really real, since they change into and out of each other. Rather, they are qualities of something more fundamental and basic, the receptacle, since it remains the same throughout the changes. The receptacle has no characteristics of its own, since it can become anything and take on any characteristic. Just as play-dough can take on any shape, in the same way the receptacle can take on any characteristics whatsoever.
As in the first version of the story, the receptacle began in chaos and disorder. The god imposed order via "shapes and numbers" (53b). This is a marked difference between Plato's story and traditional myths, which do not mention mathematics at all.
"Geometrical atomism" is how the god used 'shapes and numbers' to organize the cosmos. The ultimate building blocks of the physical universe are triangles (of various sizes, 63d). Why? Because "every surface that is rectilinear is composed of triangles," and thus every solid figure can be built up out of triangles (if we're given enough shapes and sizes). So now our question is this: what 4 solid bodies are the most perfect? These will correspond to the four elements, since the Demiurge wants to make the universe as perfect as possible. And there are five so-called perfect solids in geometry: a perfect solid is one which has the same shape on all of its faces. (So, pyramids and cubes are perfect solids; the list is on p. 58.) The fifth solid, the dodecahedron, is used for the whole Heaven, since it is most like a sphere.
Specifically -- Earth: cube; pyramid: fire; octahedron: air; icosohedron: water.
Now we have a fairly plausible account of how things change their state: their triangles are rearranged from the shape identified with water to the shape identified with air, for example.
Digestion. Fire molecules (pyramids) that we breathe in chop up our food. This is mixed with water to make blood. (Blood is red, Plato says, because there's lots of fire molecules mixed up in it -- and fire is red.) Blood then serves as the 'food' or nourishment for our bones, muscles, organs, etc.
We see the microcosm/ macrocosm analogy here (and elsewhere in the Timaeus): "The manner of this replenishment and wasting is like the movement of all things in the universe, which carries each thing toward its own kind" (81a) [the idea is that the 'bone-ish' particles in our bread, vegetables etc. will be carried to our own bones and attached there]. More directly, Plato says that our digestive processes are "constrained to reproduce the movement of the universe" (81b).
Aging. When we are young, our various fire, water, earth, and air molecules are very strong and firm: the triangles that compose them are very tightly "glued" together. As we age, the glue gets old, and the bonds start to weaken and later to break... especially when an older person's body comes into close contact with younger, and therefore firmer/ stronger molecules, which can cut those older molecules.
Disease. In general, we get sick when our bodies have too much or too little of one of the four elements in us, or if the elements are not in the proper (spatial) position. Our souls are unhealthy -- that is, we suffer from psychological disease -- when the three basic parts of our souls (reason, spirit, and appetite) are not in the proper balance, i.e., there's too much of one or the other.