In the next place, our atomic make-up involves the presence of other atomic complexes, if we are to have any psychical activity. External things must stimulate us. But these external things are atoms in action. They can, however, influence us only by coming into contact with our bodies. Only by impact on our bodies can they set in motion the fire atoms which are scattered through our bodies. Every kind of knowledge or mental life involves the participation of the fire atoms in us. Thus mental activity involves two factors; the fire atoms within us and an external group of atoms without us.
How did Democritus explain the varied mental life as the resultant of these two factors? He employed the theory of effluxes, belief in which he shared with his time. This is a purely physiological assumption, originated by such Cosmologists as Empedocles, that somehow external bodies send off emanations from themselves which strike upon our bodies. Most objects in the world influence us at a distance and only through the emission of these effluxes. Democritus conceived these emanations to be little copies or “eidola” of the thing that sends them off. To illustrate Democritus’ meaning:a tree is seen by me because little trees, thrown off by it, hit my eye. This theory retained its position in philosophical circles until after Locke. It persists in the popular mind to-day. It is a general belief that a thought is a copy, photograph, or image of the thing. The words “image” and “imagination” betray their origin. It was believed by Democritus that such copies set in motion the sense organs and through them the fire atoms. The effluxes can, however, affect only those organs of the body that have similar formation and similar atomic motions.
But the effluxes vary very much in the degree of fineness of their atomic structure. There are all sorts, from very fine to very coarse. Since the efflux must correspond to a particular sense if that sense is to be affected by it, the effluxes that can affect the senses vary respectively as to their fineness. Democritus was particularly interested in the sensations of sight and hearing as examples of this. None of the effluxes affecting the senses are as fine as those that stimulate the reason. Unless they were the finest of all the effluxes, they could not affect the fine motions of the fire atoms of the reason. These finest “eidola” or effluxes are the true copies of things, and the reason therefore alone knows things truly. Thought, on the one hand, is precisely the atomic motion of the direct impact of the finest effluxes upon the fine fire-atoms of the soul. Sensation, on the other hand, is atomic motion from the indirect impact of the coarser grades of effluxes upon the fire atoms. The reason knows reality directly. Sensations are aroused in a roundabout way by the coarse effluxes setting in motion the corresponding sense organ, which in turn sets in motion the fire atoms. Thus does Democritus make thedistinction between thought and sensation in quantitative terms. Thus does he reduce his psychology to a consistency with his metaphysical principle of materialism.
Democritus’ Theory of Knowledge—The World of Twofold Reality. Democritus would have been only one of the great Cosmologists, and he would not have his place by the side of Plato and Aristotle, if his materialism had illuminated no other subject than physics. Indeed, it is doubtful if his physics would have been so grandly comprehensive and unqualified had it not been strengthened by his discriminating theory of twofold knowledge. He might have extended and systematized his materialism so that it explained to the satisfaction of his time both physical and psychical phenomena, and still have been a hylozoist, like Leucippus, the founder of the Atomistic school. The problem of knowledge—the problem of estimating our mental states—was as incomprehensible to Leucippus as to the Eleatics. Democritus, however, was a rationalist and realist like Plato and Aristotle. He recognized, as did they, that there is a difference in epistemological values. His universalized materialism did not prevent him from evaluating our experiences from the same general point of view as the leader of the Academy and the Stagirite. He felt that a twofold reality is as consistent with materialistic principles as with idealism. So he reduced all qualities to quantities, and then as quantities re-valued and classified them. His chief contribution was to the subject of epistemology and not to physics, and that is why he is treated among the Greek Systematizers and not among the Cosmologists. Probably his chief interest lay where he did his chief work.
The perception theory of Protagoras was the starting-point of both Democritus and Plato. Both adopted it in order to transcend it and make it of real significance. Democritus, upon the basis of his materialistic psychology, admitted that sense-perception is only a transitory process, and its knowledge must be as transitory. But he did not agree with Protagoras that all knowledge is perceptual. Sense-perception does yield only relative knowledge; but there is another kind of knowledge that is not relative but absolute. This is knowledge of the reason. Human beings have reason as well as sense-perception. Thus is Democritus a rationalist, although a materialist.
The contribution of Democritus to the theory of knowledge consists in just this turn which he gave to Protagoras’ doctrine of perception. The relativity of perception becomes in the Democritan theory a different thing from what it was in the doctrine of the great Sophist. To Protagoras perceptual knowledge is relative, and therefore of no value in determining what is real. To Democritus perceptual knowledge is relative, but it has a value,—a relative value. It gets this relative value from the fact that the reason can determine absolute reality. Perception is the contributor to the reason, and also in turn is illuminated by the reason. In the same breath we may say that Protagoras was a contributor to the theory of Democritus, and in turn that the Protagorean relativism was illuminated by the Democritan rationalism. The result was a twofold knowledge—in the language of Democritus, “genuine knowledge” and “obscure insight.”
The objects corresponding to these two kinds of knowledge must be of two kinds. On the one hand,the objects of the reason, or “genuine knowledge,” are the genuine, primary, or real properties of the atoms—for the atoms are reality to Democritus.These are form, size, inertia, density, and hardness.[25] A study of these properties of things is, therefore, a study of real objects. On the other hand, the objects of perception or “obscure insight” are the properties of atoms as perceived obscurely by the senses. These are color, sound, taste, smell. They are the qualities or relative properties of things. A study of these is a study of only what is relatively real. When materialism was revived by the Renaissance, the former group of objects were called “primary qualities” and the latter “secondary qualities.” These terms have become classic, and have rendered permanent Democritus’ evaluation of the objects of the two kinds of knowledge. Out of the fragments of the teaching of the Cosmologists and the one-sided epistemology of the Sophists, Democritus constructed contemporaneously with Plato, perhaps antecedently to him, a theory of twofold knowledge.
The Ethical Theory of Democritus. The ethics of Democritus is another example of his general principle of a mechanism of atoms. His attempt to reduce all qualitative to quantitative relations, which gives his theory a unique place in Greek thought, reaches its highest distinction in his ethics. The influence of his ethical doctrine upon the Epicureans, and possibly upon the Cyrenaics, shows its importance in history. Furthermore, its high quality proves that a materialism can offer inspiring ethical doctrines. Some have placed the ethics of Democritus upon a level with the ethics of Socrates because, as it is pointed out, he placed it uponan intellectual basis. The basal ethical principle of Democritus may be stated thus: As true knowledge is the ideal object of the intellect, so true happiness is the ideal object of our conduct. The ethics of Democritus is eudæmonistic, like that of Socrates.
Pleasures have fundamental differences. They are in every case the results of atomic motions; but the atomic motions of the intellect differ from those of the senses, and those of the senses differ from one another. The fire atoms of the intellect are small, and have a gentle, peaceful motion; the atomic motions of the senses are coarse and violent, caused by the coarse effluxes of the objects that excite them. Sense-pleasures are relative, like the perceptions. As perception is obscure insight and gains the appearance and not the true reality, so the pleasures of sense are transitory, uncertain, violent, and deceitful. Intellectual pleasures are, like the intellect, real, true, permanent, gentle, and peaceful. True happiness, the goal of human activity, attends upon that right insight—upon the gentle atomic motions of the intellectual life. On the other hand, the coarse atomic motions of the senses disturb the intellectual calm, and are often violent explosions. Democritus believed that knowledge of the atoms, as the true explanation of the world, will give to the soul a measure and a harmony, will guard it from excitement and make it possessor of a peace which—to use his happy simile—is like the ocean calm. Two ideals seem to stand before Democritus, which he did not try to reconcile. Sometimes before his mind’s eye the ideal happiness is purely intellectual pleasure and points toward asceticism. Sometimes he speaks of happiness as the life of perfect self-control and temperance. He never positively deniesall value to sense-pleasure, but he gives to sense-pleasure the relative value that he gives to the senses themselves. In every case the ground of happiness is intellectual refinement, and the ground of unhappiness the lack of it. The majority of men are sensualists and are to be contrasted with the Wise Man, who finds his happiness either in his individual life or in his friendship with other Wise Men.