Anaxagoras raised two objections against Parmenides:
  1. the origin of semblance, and
  2. the mobility of thought.
He did not object, however, to Parmenides's main doctrine that there is only being, not becoming. Anaximander and Heraclitus had claimed that there is becoming and passing away. Thales and Heraclitus had said that the world of multiple qualities comes out of one prime substance. With Anaxagoras, all subsequent philosophers and scientists rejected all coming into existence out of nothing and disappearance into nothing.
If the many things that we experience in the world are not mere semblance but do not come from nothing and do not come from one single thing, what is their origin? Since like produces like, the many different things come from many different things. In other words, there are infinitely many different prime substances. Their total is always constant but their arrangements change.
Why do the forms and patterns of these real substances change? Because they are in motion. Change and motion are not semblance and are truly real. Does the movement come from within each thing? Is there another external thing that moves each object?
Movement is not mere appearance. Movement occurs because each substance is similar to each other substance in that they are all made of the same matter. There is no total isolation or complete difference between substances. This common material substratum allows them to interact. When two substances try to occupy the same space, one of the substances must move away. This is actual motion and change.
If it is certain that our ideas appear to us in succession, then they must move themselves because they are not moved by things that are not ideas. This proves that there is something in the world that moves itself. Ideas are also capable of moving things that are different from themselves. They move the body. Therefore, there is a thinking substance that moves itself and other substances. This nous (mind, intelligence) is made out of extremely fine and delicate matter. It is an ordering, knowing, purposeful mover. Nous was the first cause of every subsequent mechanical change in the universe.
Originally, before nous moved the first particle of matter, there was a complete mixture which was composed of infinitely small components of things. Each of these was a homoeomery, the small parts being the same as the large whole. For example, a tooth is made of small teeth. This is the result of the thought that like must come from like. After the movement began, individual objects became separated from this mixture when like combined with like. When one substance finally predominated, the accumulation became a particular thing. This process is called "coming to be" or "becoming."
Nous is not a part of the original mixture. It started the revolutionary motion which separated things from the primal mixture. The motion is a centrifugal, spiralling vortex in which likes attach to their likes. There is no god who moves things with a purpose in mind. There is only a mechanical whirlpool of movement. Unlike Parmenides's motionless sphere of being, Anaxagoras saw the world as a moving circle of becoming. Nous started the spinning. Thereafter the universe developed on its own, according to lawful necessity.
To be able to start and sustain motion against the resistance of the infinite mixture, nous had to use a sudden, infinitely strong and infinitely rapid, force. It also had to move the first point in a circular path that was larger than its own size. In this way, it affected other points. Nous freely chose to start the vortex. It thereby created its own goal and purpose in a playful game. This was not a moral or ethical process. Rather, it was aesthetic, in that nous simply wanted to enjoy the spectacle of its own creation.
Later philosophers, such as Plato, wanted to attribute ethical properties to nous's creation of the world. For them, it should be made in the most perfect, beautiful, useful manner. Anaxagoras, however, did not employ teleology. Nous, for him, was a mechanical, efficient cause, not a final cause. Any future purpose would have eliminated a freely chosen start.
Nietzsche's book abruptly ends here with a description of a nous that created the world as a game. The freedom of nous's creative will is opposed to the necessary determinism of its creation, the universe. Nous is referred to as a mind (Geist) that has free, arbitrary choice. The created world, physis, is a determined, mechanical piece of machinery. Any order or efficiency of things is only an outcome of purposeless change.