Anaxagoras held that the universe is infinite in extent and composed of mind and matter, but mind is a special kind of matter. There is no empty space.

Matter is not composed of primary units; it is infinitely divisible. “Nor is there a least of what is small, but there is always a smaller; for it cannot be that what exists should cease to be by being cut.” If you take a piece of a certain kind of matter—a hair, say, or a steak—and begin cutting, no matter how finely you cut it the pieces will still have the characteristics of hair or flesh. “How can hair come from what is not hair, or flesh from what is not flesh?”

Nevertheless, we eat bread, and the bread (we say) becomes hair and flesh. This is not accurate, Anaxagoras says: “The Greeks follow a wrong usage in speaking of coming into existence and passing away; for nothing comes into existence or passes away, but there is mingling and separation of things that exist. Therefore, they would be right to call coming into existence mixture, and passing away separation.” The “coming into existence” of the hair is really mixture, then, and the “passing away” of the bread is separation. However, this prompts one to ask: Mixture and separation of what? Any crumb of bread, however tiny, has all the properties of the whole loaf. Bread is not made of bits of hair and flesh. Likewise a hair is not separable into microscopic breadcrumbs. How then can hair be a “mixture” into which bread enters, while at the same time it cannot “come from what is not hair”?

The answer is that “The things that are in one world are not divided nor cut off from one another with a hatchet.” Although bread contains no particles of hair, it nevertheless contains hair fused or dissolved in it. In general, “all things will be in everything; nor is it possible for them to be apart, but all things have a portion of everything. . . . And in all things many things are contained, and an equal number both in the greater and in the smaller of the things that are separated.”

A loaf of bread contains “portions of everything”; that is, it contains or rather is a complex of all the sensible qualities. The same is true of every crumb of the loaf. (Anaxagoras was notorious for asserting that snow is black—in the sense that even the purest white stuff yet contains a portion of every “thing,” including blackness.) Yet the loaf does not appear to our senses as a primordial chaos. “Each single thing is most manifestly those things of which it has most in it.” It presents us with a definite, restricted set of qualities, such as brownness, moisture, bread-smell, and bread-taste. Hair as we know it is black, shiny, oily. Hair is in bread in the sense that blackness, shininess, and oiliness are all there, but relatively in such small quantities that “the weakness of our senses prevents our discerning the truth.” If we were presented (per impossibile) with a loaf of “pure” bread, we could not distinguish it from an ordinary loaf by looking at it, smelling it, or tasting it; but it would not nourish us. Our insides, however, are able (in an unexplained manner) to separate out the traces of hair and flesh.

Anaxagoras used the word “seeds”—”seeds of all things, having all sorts of characteristics both of color and of savor,” “a multitude of innumerable seeds in no way like each other”—to indicate the diversity of quality-things to be found in even the smallest bit of matter. However, the word has no atomistic implications; anything, however large or small, that has a trace of hair in it is a hair “seed.” The word occurs only twice in the extant fragments, both times in a description of world formation, and all that is signified is that the original mixture of all things has the potentialities in it for eventual separation into the most diverse kinds of objects.

Mind, like blackness or the smell of bread, is a real stuff; consequently, it has location (“it is certainly there, where everything else is”) and occupies space (“it is the thinnest of all things and the purest”). Although this seems sufficient evidence to make it a kind of matter, it must be remembered that Anaxagoras does not make a distinction between stuff and the qualities of stuff; indeed, refusal to make this distinction is the key to his philosophy. Mind has or is the properties that in our experience we find it to have: It is conscious and cognitive (“it has all knowledge about everything”) and powerful, manifesting itself as will power or élan vital in living things (“mind has the greatest strength; and it has power over all things, both greater and smaller, that have life”). It is unique in not entering into mixtures: “All other things partake in a portion of everything, while Mind is infinite and self-ruled, and is mixed with nothing but is alone, itself by itself.” Anaxagoras argued that “if it were not by itself, but were mixed with anything else, it would partake in all things if it were mixed with any; for in everything there is a portion of everything, and the things mixed with it would hinder it, so that it would have power over nothing in the same way that it has now being alone by itself.” The thought seems to be that if mind mixed, it would lose its peculiar power just as the blackness in snow or the breadness in hair does; but this is impossible, both because what is essentially active cannot become passive and because our minds are experienced as unities. Also “it would partake in all things if it were mixed with any”; rocks and clods would be alive—an absurdity.

However, although mind is not mixed with anything, it is present in some living things: “In everything there is a portion of everything except Mind, and there are some things in which there is Mind also.” The power of mind is to initiate activity (motion) in these things and to move and “set in order all things” from outside. Anaxagoras also says “All Mind is alike, both the greater and the smaller.” It is the same mind stuff that is present in people as in other animals and vegetables. Humans’ greater intelligence is due not to possession of a superior grade of mind but to our having hands.