All atoms essentially separate from each other.

All properties of objects, except weight and hardness, were phenomenal and relative to the observer. Sensation could give no knowledge of the real and absolute.

Pursuant to this theory, Demokritus proclaimed that all the properties of objects, except weight, hardness, and softness, were not inherent in the objects themselves, but simply phenomenal and relative to the observer — “modifications of our sensibility”. Colour, taste, smell, sweet and bitter, hot and cold, &c., were of this description. In respect to all of them, man differed from other animals, one man from another, and even the same man from himself at different times and ages. There was no sameness of impression, no unanimity or constancy of judgment, because there was no real or objective “nature” corresponding to the impression. From none of these senses could we at all learn what the external thing was in itself. “Sweet and bitter, hot and cold (he said) are by law or convention (i.e. these names designate the impressions of most men on most occasions, taking no account of dissentients): what really exists is, atoms and vacuum. The sensible objects which we suppose and believe to exist do not exist in truth; there exist only atoms and vacuum. We know nothing really and truly about an object, either what it is or what it is not: our opinions depend upon influences from without, upon the position of our body, upon the contact and resistances of external objects. There are two phases of knowledge, the obscure and the genuine. To the obscure belong all our senses — sight, hearing, smell, taste, touch. The genuine is distinct from these. When the obscure phase fails, when we can no longer see, nor hear, nor smell, nor taste, nor touch — from minuteness and subtlety of particles — then the genuine phase, or reason and intelligence, comes into operation.”210

Reason alone gave true and real knowledge, but very little of it was attainable.

True knowledge (in the opinion of Demokritus) was hardly at all attainable; but in so far as it could be attained, we must seek it, not merely through the obscure and insufficient avenues of sense, but by reason or intelligence penetrating to the ultimatum of corpuscular structure, farther than sense could go. His atoms were not pure Abstracta (like Plato’s Ideas and geometrical plane figures, and Aristotle’s materia prima), but concrete bodies, each with its own211 magnitude, figure, and movement; too small to be seen or felt by us, yet not too small to be seen or felt by beings endowed with finer sensitive power. They were abstractions mainly in so far as all other qualities were supposed absent. Demokritus professed to show how the movements, approximations, and collisions of these atoms, brought them into such combinations as to form the existing Kosmos; and not that system alone, but also many other cosmical systems, independent of and different from each other, which he supposed to exist.

No separate force required to set the atoms in motion — they moved by an inherent force of their own. Like atoms naturally tend towards like. Rotatory motion, the capital fact of the Kosmos.

How this was done we cannot clearly make out, not having before us the original treatise of Demokritus, called the Great Diakosmos. It is certain, however, that he did not invoke any separate agency to set the atoms in motion — such as the Love and Discord of Empedokles — the Nous or Intelligence of Anaxagoras. Demokritus supposed that the atoms moved by an inherent force of their own: that this motion was as much without beginning as the atoms themselves:212 that eternal motion was no less natural, no more required any special cause to account for it, than eternal rest. “Such is the course of nature — such is and always has been the fact,” was his ultimatum.213 He farther maintained that all the motions of the atoms were necessary — that is, that they followed each other in a determinate order, each depending upon some one or more antecedents, according to fixed laws, which he could not explain.214 Fixed laws, known or unknown, he recognised always. Fortune or chance was only a fiction imagined by men to cover their own want of knowledge and foresight.215 Demokritus seems to have supposed that like atoms had a spontaneous tendency towards like; that all, when uncombined, tended naturally downwards, yet with unequal force, owing to their different size, and weight proportional to size; that this unequal force brought them into impact and collision one with another, out of which was generated a rotatory motion, gradually extending itself, and comprehending a larger and larger number of them, up to a certain point, when an exterior membrane or shell was formed around them.216 This rotatory motion was the capital fact which both constituted the Kosmos, and maintained the severance of its central and peripheral masses — Earth and Water in the centre — Air, Fire, and the celestial bodies, near the circumference. Demokritus, Anaxagoras, and Empedokles, imagined different preliminary hypotheses to get at the fact of rotation; but all employed the fact, when arrived at, as a basis from which to deduce the formation of the various cosmical bodies and their known manifestations.217 In respect to these bodies — Sun, Moon, Stars, Earth, &c. — Demokritus seems to have held several opinions like those of Anaxagoras. Both of them conceived the Sun as a redhot mass, and the Earth as a flat surface above and below, round horizontally like a drum, stationary in the centre of the revolving celestial bodies, and supported by the resistance of air beneath.218

Researches of Demokritus on zoology and animal generation.

Among the researches of Demokritus there were some relating to animal generation, and zoology; but we cannot find that his opinions on these subjects were in peculiar connection with his atomic theory.219 Nor do we know how far he carried out that theory into detail by tracing the various phenomenal manifestations to their basis in atomic reality, and by showing what particular magnitude, figure, and arrangement of atoms belonged to each. It was only in some special cases that he thus connected determinate atoms with compounds of determinate quality; for example, in regard to the four Empedoklean elements. The atoms constituting heat or fire he affirmed to be small and globular, the most mobile, rapid, and penetrating of all; those constituting air, water, and earth, were an assemblage of all varieties of figures, but differed from each other in magnitude — the atoms of air being apparently smallest, those of earth largest.220

His account of mind — he identified it with heat or fire diffused throughout animals, plants, and nature generally. Mental particles intermingled throughout all the frame with corporeal particles.

In regard to mind or soul generally, he identified it with heat or fire, conceiving it to consist in the same very small, globular, rapidly movable atoms, penetrating everywhere: which he illustrated by comparison with the fine dust seen in sunbeams when shining through a doorway. That these were the constituent atoms of mind, he proved by the fact, that its first and most essential property was to move the body, and to be itself moved.221 Mind, soul, the vital principle, fire, heat, &c., were, in the opinion of Demokritus, substantially identical — not confined to man or even to animals, but diffused, in unequal proportions, throughout plants, the air, and nature generally. Sensation, thought, knowledge, were all motions of mind or of these restless mental particles, which Demokritus supposed to be distributed over every part of the living body, mingling and alternating with the corporeal particles.222 It was the essential condition of life, that the mental particles should be maintained in proper number and distribution throughout the body; but by their subtle nature they were constantly tending to escape, being squeezed or thrust out at all apertures by the pressure of air on all the external parts. Such tendency was counteracted by the process of respiration, whereby mental or vital particles, being abundantly distributed throughout the air, were inhaled along with air, and formed an inward current which either prevented the escape, or compensated the loss, of those which were tending outwards. When breathing ceased, such inward current being no longer kept up, the vital particles in the interior were speedily forced out, and death ensued.223

Different mental aptitudes attached to different parts of the body.

Though Demokritus conceived those mental particles as distributed all over the body, yet he recognised different mental aptitudes attached to different parts of the body. Besides the special organs of sense, he considered intelligence as attached to the brain, passion to the heart, and appetite to the liver:224 the same tripartite division afterwards adopted by Plato. He gave an explanation of perception or sensation in its different varieties, as well as of intelligence or thought. Sensation and thought were, in his opinion, alike material, and alike mental. Both were affections of the same peculiar particles, vital or mental, within us: both were changes operated in these particles by effluvia or images from without; nevertheless the one change was different from the other.225

In regard to sensations, Demokritus said little about those of touch, smell, and hearing; but he entered at some length into those of sight and taste.226

Explanation of different sensations and perceptions. Colours.

Proceeding upon his hypothesis of atoms and vacua as the only objective existences, he tried to show what particular modifications of atoms, in figure, size, and position, produced upon the sentient the impressions of different colours. He recognised four fundamental or simple colours — white, black, red, and green — of which all other colours were mixtures and combinations.227 White colour (he said) was caused by smooth surfaces, which presented straight pores and a transparent structure, such as the interior surface of shells: where these smooth substances were brittle or friable, this arose from the constituent atoms being at once spherical and loosely connected together, whereby they presented the clearest passage through their pores, the least amount of shadow, and the purest white colour. From substances thus constituted, the effluvia flowed out easily, and passed through the intermediate air without becoming entangled or confused with it. Black colour was caused by rough, irregular, unequal substances, which had their pores crooked and obstructed, casting much shadow, and sending forth slowly their effluvia, which became hampered and entangled with the intervening medium of air. Red colour arose from the effluvia of spherical atoms, like those of fire, though of larger size: the connection between red colour and fire was proved by the fact that heated substances, man as well as the metals, became red. Green was produced by atoms of large size and wide vacua, not restricted to any determinate shape, but arranged in peculiar order and position. These four were given by Demokritus as the simple colours. But he recognised an infinite diversity of compound colours, arising from mixture of them in different proportions, several of which he explained — gold-colour, purple, blue, violet, leek-green, nut-brown, &c.228

Vision caused by the outflow of effluvia or images from objects. Hearing.

Besides thus setting forth those varieties of atoms and atomic motions which produced corresponding varieties of colour, Demokritus also brought to view the intermediate stages whereby they realised the act of vision. All objects, compounds of the atoms, gave out effluvia or images resembling themselves. These effluvia stamped their impression, first upon the intervening air, next upon the eye beyond: which, being covered by a fine membrane, and consisting partly of water, partly of vacuum, was well calculated to admit the image. Such an image, the like of which any one might plainly see by looking into another person’s eye, was the immediate cause of vision.229 The air, however, was no way necessary as an intervening medium, but rather obstructive: the image proceeding from the object would be more clearly impressed upon the eye through a vacuum: if the air did not exist, vision would be so distinct, even at the farthest distance, that an object not larger than an ant might be seen in the heavens.230 Demokritus believed that the visual image, after having been impressed upon the eye, was distributed or multiplied over the remaining body.231 In like manner, he believed that, in hearing, the condensed air carrying the sound entered with some violence through the ears, passed through the veins to the brain, and was from thence dispersed over the body.232 Both sight and hearing were thus not simply acts of the organ of sense, but concurrent operations of the entire frame: over all which (as has been already stated) the mental or vital particles were assumed to be disseminated.

Differences of taste — how explained.

Farther, Demokritus conceived that the diversities of taste were generated by corresponding diversities of atoms, or compounds of atoms, of particular figure, magnitude and position. Acid taste was caused by atoms rough, angular, twisted, small, and subtle, which forced their way through all the body, produced large interior vacant spaces, and thereby generated great heat: for heat was always proportional to the amount of vacuum within.233 Sweet taste was produced by spherical atoms of considerable bulk, which slid gently along and diffused themselves equably over the body, modifying and softening the atoms of an opposite character. Astringent taste was caused by large atoms with many angles, which got into the vessels, obstructing the movement of fluids both in the veins and intestines. Salt taste was produced by large atoms, much entangled with each other, and irregular. In like manner Demokritus assigned to other tastes particular varieties of generating atoms: adding, however, that in every actual substance, atoms of different figures were intermingled, so that the effect of each on the whole was only realised in the ratio of the preponderating figure.234 Lastly, the working of all atoms, in the way of taste, was greatly modified by the particular system upon which they were brought to act: effects totally opposite being sometimes produced by like atoms upon different individuals.235

Thought or Intelligence — was produced by influx of atoms from without.

As sensation, so also thought or intelligence, was produced by the working of atoms from without. But in what manner the different figures and magnitudes of atoms were understood to act, in producing diverse modifications of thought, we do not find explained. It was, however, requisite that there should be a symmetry, or correspondence of condition between the thinking mind within and the inflowing atoms from without, in order that these latter might work upon a man properly: if he were too hot, or too cold, his mind went astray.236 Though Demokritus identified the mental or vital particles with the spherical atoms constituting heat or fire, he nevertheless seems to have held that these particles might be in excess as well as in deficiency, and that they required, as a condition of sound mind, to be diluted or attempered with others. The soundest mind, however, did not work by itself or spontaneously, but was put in action by atoms or effluvia from without: this was true of the intellectual mind, not less than of the sensational mind. There was an objective something without, corresponding to and generating every different thought — just as there was an objective something corresponding to every different sensation. But first, the object of sensation was an atomic compound having some appreciable bulk, while that of thought might be separate atoms or vacua so minute as to be invisible and intangible. Next, the object of sensation did not reveal itself as it was in its own nature, but merely produced changes in the percipient, and different changes in different percipients (except as to heavy and light, hard and soft, which were not simply modifications of our sensibility, but were also primary qualities inherent in the objects themselves237): while the object of thought, though it worked a change in the thinking subject, yet also revealed itself as it was, and worked alike upon all.

Sensation, obscure knowledge relative to the sentient; Thought, genuine knowledge — absolute, or object per se.

Hence Demokritus termed sensation, obscure knowledge — thought, genuine knowledge.238 It was only by thought (reason, intelligence) that the fundamental realities of nature, atoms and vacua, could be apprehended: even by thought, however, only imperfectly, since there was always more or less of subjective movements and conditions, which partially clouded the pure objective apprehension — and since the atoms themselves were in perpetual movement, as well as inseparably mingled one with another. Under such obstructions, Demokritus proclaimed that no clear or certain knowledge was attainable: that the sensible objects, which men believed to be absolute realities, were only phenomenal and relative to us, — while the atoms and vacua, the true existences or things in themselves, could scarce ever be known as they were:239 that truth was hidden in an abyss, and out of our reach.

Idola or images were thrown off from objects, which determined the tone of thoughts, feelings, dreams, divinations, &c.

As Demokritus supposed both sensations and thoughts to be determined by effluvia from without, so he assumed a similar cause to account for beliefs, comfortable or uncomfortable dispositions, fancies, dreams, presentiments, &c. He supposed that the air contained many effluences, spectres, images, cast off from persons and substances in nature — sometimes even from outlying very distant objects which lay beyond the bounds of the Kosmos. Of these images, impregnated with the properties, bodily and mental, of the objects from whence they came, some were beneficent, others mischievous: they penetrated into the human body through the pores and spread their influence all through the system.240 Those thrown off by jealous and vindictive men were especially hurtful,241 as they inflicted suffering corresponding to the tempers of those with whom they originated. Trains of thought and feeling were thus excited in men’s minds; in sleep,242 dreams, divinations, prophetic warnings, and threats, were communicated: sometimes, pestilence and other misfortunes were thus begun. Demokritus believed that men’s happiness depended much upon the nature and character of the images which might approach them, expressing an anxious wish that he might himself meet with such as were propitious.243 It was from grand and terrific images of this nature, that he supposed the idea and belief of the Gods to have arisen: a supposition countenanced by the numerous tales, respecting appearances of the Gods both to dreaming and to waking men, current among the poets and in the familiar talk of Greece.