§ 16.
1. While the Atomists, in their purely mechanical theory of external nature, were constructing a system of thorough-going materialism, Anaxagoras, adopting the notion of a mechanism in nature, was developing upon this basis the Dualism already outlined by Empedocles, and was thereby bringing about the transition from the mere philosophy of nature to the higher Ideal Philosophy of the Attic school.
2. Anaxagoras was born of a distinguished family of Clazomenae, in Asia Minor, about B.C. 500. In his later life he removed to Athens, where he lived in intimacy with Euripedis and Pericles, till the political rivals of the latter made the opinions of the philosopher the ground of a charge of impiety against him. To escape the results of the prosecution, Anaxagoras retired to Lampsacus, where he soon after died. He is the author of a treatise, peri phuseôs, of which Plato (Phaedo, p. 97) makes mention.
3. The theory of Anaxagoras regarding external nature rests upon five main principles: --
There is no beginning of things and no dissolution, in the strict sense of these terms. Nothing comes out of nothing. All that begins to be must come from something already existing. What we call the origin of things and their dissolution depends entirely upon a conjunction (sugkrisis) and a separation (diakrisis) of parts previously existing.
There are bodies which consist of homogeneous parts, and bodies of which the parts are heterogeneous. The constituent parts which unite to form bodies are not all of the same nature; a radical difference exists between them, and this difference is primary, original, not secondary or derivative.
Again, each of the various constituent parts of which bodies consist is itself constituted by smaller homogeneous parts, so minute as to be indivisible. These minute parts differ from the whole into which they enter, in quantity only, not in quality.
Hence it follows that primary matter, the causa materialis from which all things come, is an infinite multitude of infinitesimally small particles, not specifically alike, but distinguished by essential differences of nature. These primary particles, thus distinguished (chrêmata), must be regarded as the ultimate constituents, the "seeds" (spermata) of all things.
From these ultimate constituents material bodies are thus formed: Homogeneously constituted bodies, i.e., those whose constituent parts are all of like nature, as for example, Flesh, Blood, Bone, Gold, Silver, &c. are composed of primitive particles, like in kind to one another, homoeomeriae (homoiomeriai); heterogeneously constituted bodies, on the other hand, i.e., those whose parts differ in kind from one another, as, for example, organic structures, are composed of primary particles differing in kind.{1}
4. This being premised, Anaxagoras proceeds to explain the process of the world's formation: --
At first the primary particles, or "seeds," of things were promiscuously mixed together in one common mass, and as a consequence of this mixture, no one of them could exhibit itself in its proper specific character. Before the world could be formed, a separation of the primitive particles -- homoeomeriae -- had to be effected. On no other condition could they unite for the formation of the bodies which now actually exist.
The cause of this separation, and of the various subsequent combinations of primitive particles, was not in the primary matter itself, for material particles do not, of their own accord, separate or enter into union. We are therefore forced to admit a cause higher than matter, but exerting an influence upon it, and by this influence effecting the separation of the primary particles and their subsequent combinations. And since everything in the world is formed and arranged in accordance with a definite plan, and plan and order suppose Reason, it follows that the efficient cause which presides over matter must be Mind (nous).
We have here two distinct principles contributing to the formation of the world, the material -- a medley of all the "seeds" of things, and the efficient -- the spirit or mind (nous). This is the dualistic doctrine in all plainness. According to the teaching of Anaxagoras, Mind is distinguished from Matter by its simplicity, its independence, its knowledge, and its control over matter. All things else have some admixture of the particles of all other things; the mind alone is pure, unmixed, subject only to itself, the most subtle of all things. The formation of the world was brought about by motion. After the primary matter had rested in its inertness through countless ages, it was at last set in motion by the Divine Mind, and by this motion the world was evolved from chaos. This movement was a movement of rotation, established by the Mind at a single point, but gradually taking in further and further masses, and extending its range through the infinitude of matter. Everywhere, however, this movement follows a definite plan, everything in the world is formed and disposed for a purpose, there is no Fate (eimarmenê), no Chance (tuchê).{2}
In consequence of the revolving motion, "Air and Ether were separated from the primary mass, and filled all space -- there is no such thing as a vacuum -- contrary elements, the rarefied and the dense, the hot and the cold, the bright and the gloomy, the moist and the dry, were severally separated from each other; the dense, the cold, the gloomy, and the damp sank to the region now occupied by the earth, while the others mounted to the sphere of the ether. Here they formed hard stony masses, which, set in due order, and raised by the revolving movement to a white heat, became stars; while, far below, the elements that had fallen downwards became solidified into earth and stones." The earth rests in the middle of the world. It is shaped like a short cylinder, and is borne up by the air. Plants and animals owe their being to the germs which the earth, while yet moist and slimy, received from the air, and which were developed in the bosom of the earth under the influence of celestial heat. Once brought into being they continued to propagate themselves.
5. Everywhere in his Cosmogony, Anaxagoras is careful to make the Mind pre-eminent, to keep it aloof from the processes of nature; the latter he strives to account for solely by that movement originally impressed upon things by the nous. In his psychology, on the other hand, he shows no disposition of this kind. On the contrary, in his explanation of the psychical element in living beings, he feels driven to assume the indwelling in them of the (Divine) Mind, and so to make Mind the psychical principle of all living things. Whilst then the nous in its relation to the Makrokosmos is merely an external motive force, in relation to organic beings it assumes the character of an intrinsic psychical principle. Moreover, its functions in the latter respect are not confined to men and animals, they extend to plants also; for they too, in the opinion of Anaxagoras, are animated, and have their joys and their sorrows. The "Soul" of the living thing is perfect in proportion to the perfection of the corporeal organism with which it is associated, or, to express the same thing in the language of Anaxagoras, the Divine Spirit manifests itself in the living thing in proportion as the organism is perfect. It follows that the most perfect ("greatest") soul is possessed by man; that in him God manifests himself most fully.
The sense-faculties of man are too weak to attain to truth; they are unable to distinguish sufficiently between the constituent elements of things. It is Mind that attains knowledge of things. All things are known to the Divine Reason; the mind of man, being a factor of the Divine Mind, can therefore attain to knowledge. The highest contentment is to be found in the knowledge of the universe obtained by thought. Whatever is good, just, or beautiful, is to be ascribed to the Spirit or Mind; evil, moral and physical, is from matter.
7. Along with Anaxagoras, we may include among the philosophers of Nature, Hermotimus of Clazomenae (whom some writers make the teacher of Anaxagoras), who is said to have held similar views regarding the world-ordering mind; and Archelaus, the physicist (of Miletus, or, according to others, of Athens) a pupil of Anaxagoras, who seems to have held the primary mixture of all things to be equivalent to Air, and who also seems to have laid less stress on the contrasts between mind and matter, and thus to have again approached the teaching of the older Ionians. He is credited with the doctrine that the distinction between Right and Wrong is not founded on the nature of things (phusei) but is of human institution (nomô). Metrodorus, of Lampsacus, was also a disciple of Anaxagoras. He is known by his allegorical interpretation of the Homeric Myths.
{1} Homogeneously constituted bodies were called by Aristotle homoiomerê in contradistinction to the heterogeneously constituted, anomoiomerê. These terms, originally applied to fully constituted bodies, were transferred to the constituent elements of the bodies. In this way the elements, or "seeds," of the homogeneous bodies of Anaxagoras came to be designated homoiomerê by Aristotle. Anaxagoras himself does not appear to have used the term.
{2} It is, however, worthy of remark that Anaxagoras avoids the application of this principle of design in nature to particular cases. Individual phenomena he almost always tries to explain by purely physical causes, without recurrence to the plan of the Divine Mind -- a procedure on which Plato and Aristotle comment unfavourably. Aristotle (Met. 1. 4.) reproaches him with making the nous a Deus ex machina, which he calls upon only when he is at a loss to find the natural cause of some phenomenon.