Anaxagoras, also born near Miletus but then living in Athens for a time, agrees with Empedocles, his contemporary, that Parmenides was right about change: all that we call change is just a re-arranging. But nothing actually comes out of nothing or passes into nothing, for no-thing does not exist and so this is impossible. For Empedocles, bone for example, would be made up of a certain ratio of earth, water, air and fire. But Anaxagoras showed this to be false: if the ratio is disturbed, then the elements are no longer bone, and so bone really does pass out of existence. Instead, Anaxagoras held that a bone, such as a femur, is made of bone matter. The Smallest particle is bone. Bone is made up of small bones; flesh is made up of miniature flesh, and so forth. These elements are eternal and have always existed.
But this presents a problem: when a child eats bread and milk, and grows hair and larger bones, how does bone come from what is not bone? His answer is that bread and milk and all food contains little bits of bone and hair and so forth. This leads to his larger thesis that “In everything there is a portion of everything.”
In addition to matter being described thus so, Anaxagoras posits Mind, Logos, which controls nature. Plato records Socrates telling of his interest in the natural philosophers in his youth, and then coming across Anaxagoras, and being very excited by his description of Mind. For, Socrates says, “I was delighted with this; it seemed somehow right that Mind should be the cause of all things, and I thought that if this were the case then Mind, in arranging all things, would arrange things in the way that was best for it.” (Phaedo, 97B).
This is getting ahead of ourselves, but do you see the huge metaphysical jump forward that Socrates makes here in his reflection on Anaxagoras? Mind would arrange matter in a way that is best for it. Best? How do you get an evaluation, a value at all, out of atoms or particles? If some particles gather and form a bone and then the bone decays and those particles disperse, what is good or bad about that? From a materialist perspective, it is value-less. It is just a datum, a fact, something to be observed or described. . . but not evaluated. For something to be evaluated, it is deemed good or bad, better or worse, best or worst. Where do these value judgements come from? The young Socrates longed for a philosophical account of what is best for things. And yet the natural philosophers could not provide it. Anaxagoras did, it is true, posit Mind. But Socrates is disappointed to discover that after mentioning it, he rarely refers to it, describing most of reality in terms of the arrangement of the elements.