Popular Science Monthly/Volume 18/April 1881/An Ancient Scientist


READERS of Mrs. Browning will remember in the "Vision of Poets" the description of Lucretius, as one

"Who dropped his plummet down the broad,

Deep universe, and said, 'No God,'

"Finding no bottom. He denied
Divinely the Divine, and died

Chief poet by the Tiber side."

In spite of this high encomium, approved by men of taste in all ages, the subject of this sketch is far less known to fame than many others of much smaller ability either as poets or as philosophers. He is unknown to many, to whom Virgil, Horace, Juvenal, and even Ovid, are household words. And yet, of these four, Virgil alone can contest the palm of supremacy with him. When Tyndall, in his famous Belfast Address, introduced his typical Lucretian as an opponent to Bishop Butler, many well-informed people were driven to their classical dictionaries to discover whom the orator meant.

It is not easy to say what are the causes of this neglect, Lucretius is not only one of the few first-class poets in Latin literature, but he is also one of the most subtile and original thinkers that Rome ever produced. His system shows how far scientific speculation had gone in his day, and what views the most enlightened took in regard to the structure of the universe and the problems of matter and life. His theories are plausible, and sometimes have anticipated modern hypotheses and discoveries. Yet few really know who he was and what his doctrines are. It is to supply this wanting knowledge—to show what relation Lucretius actually bears to science—that this summary of his principles was written.

Titus Lucretius Carus was born 96 b. c., and was thus the contemporary of Cicero, Cæsar, and Sallust. As with many other great men, little of his personal life is known. It appears that in his youth he studied philosophy at Athens in company with Cicero and other Romans afterward distinguished in politics and literature. Beyond this we know nothing certain of his life. He died b. c. 52, while Horace was still a schoolboy at Rome and Virgil had just reached the age of manhood. There is a story that his wife, fearing a decrease in his affection toward her, had given him a love-philter, which made havoc with his brain, and filled his mind with base thoughts, so that sooner than endure them he killed himself. This version of his death is well known through Tennyson's poem "Lucretius"; it, however, is a matter of tradition, and not of history.

From his life we now turn to his great work, "The Nature of Things." In this he lays down the whole system of the Epicurean philosophy, a system which has been more vilified and misrepresented than any other put forth by man. Its physical basis was the atomic theory, which was first promulgated by Leucippus. The real founder of the school was Democritus of Abdera, to whom Bacon awards a high place among great thinkers. The great exponent of these doctrines was Epicurus, from whom the system takes its name. He lived mostly at Athens in the third and fourth centuries before Christ, and was noted for his frugal and virtuous life. His moral principles did not consist in reckless indulgence of the senses, but in moderation in all things, and in avoidance of pain, whether moral, mental, or physical. This principle is continually set forth and illustrated by Horace, especially in his "Satires." In him the tenets of the Epicurean philosophy become the maxims of a prudent, intelligent man of the world.

But it is with the scientific aspect of this system, as set forth by Lucretius, that we have chiefly to do. Its principles are contained in six books of twelve or thirteen hundred lines apiece. It is best to take up the books in their order, as the argument is closely connected throughout.

The first book contains the broad principles of the atomic theory. After a beautiful passage describing the benumbing power of superstition, he asserts that the only means of overcoming this is found in the study of nature, and declares that the difficulty of the task shall not prevent him from attempting it. The first principle which he lays down is, that all matter is uncreated; or, as he expresses it, nothing can spring from nothing. For, if anything can spring from nothing, what need is there of these long processes of birth and growth and these aids to development? Why should all this labor be spent in vain, if anything could become what it is without labor? This is simply the ordinary scientific argument from experience, and, although not strictly logical, is an expression of the conviction, common to every student of Nature, of the continuity and permanence of physical law. This conviction is not supported by arguments, but is built up slowly and surely by the daily observation of Nature’s working and of the never-failing fulfillment of her laws. Our author's reasoning, therefore, is calculated rather to convince the man of science than the mere logician.

Having established this principle, he goes on to state the converse, that matter is never annihilated. For, he argues, since nothing can be created, a continual unreplaced loss would have been going on, which in the infinite course of past time would have left nothing of the universe at all. Here, again, he shows that he has the scientific conviction of the uniformity of nature. An objector might have said, “Though there has been no loss, no annihilation in time past, how do you know that there will be none in time future?” This argument, though unanswerable, is incapable of producing conviction in a scientific mind. Such an argument, as Tyndall remarks in his “Fragments of Science,” is employed by the spiritualists in regard to the sun's failing to rise on the morrow. “Before such a state of mind,” says he, “the scientific intellect is absolutely powerless.” The convictions that rise from uniform experience in the pursuit of physical studies are unassailable by any reasoning short of a mathematical demonstration.

Lucretius adds that, in many cases of apparent annihilation, matter is but lost to grow again in another form. He instances the rain whose drops fall upon the ground and are scattered, but appear again in the blooming tree which shelters beneath its branches flocks and herds and the race of men. Here, as often with this poet, a beautiful episode crops out in the midst of his philosophical argument. Indeed, it is one of his characteristics, and forms his claim to be considered a great poet, that, combined with his appreciation of the order and continuity of nature, he has a fervent love for all its aspects of beauty and life. Often he turns aside to tell of frisking lambs and babbling brooks, and trees that spread their branches far and wide. He seems to have loved nature in all its forms, and to have devoted to it all the wealth of his intellect and imagination. He closes this argument with the celebrated saying, “Nature builds up one thing by means of another, and suffers nothing to be born except another die.”

These two propositions, that nothing is created and nothing destroyed, are the primary postulates upon which as a foundation he builds the whole theory of atoms. His first step is to show that there are bodies, which, though invisible, are yet appreciable through the senses. The air, he argues, must consist of solid particles in as true a sense as water, for water itself can not produce greater effects than violent winds. There are, too, other particles of matter which affect the other senses, but not that of sight. This is proved by the sensations of sound, heat, and smell, which must be produced by matter, for to give rise to the feeling of touch is the essential property of matter and of matter alone. This property is what he calls an officum corporis—that is, a “function of substance”; another which he mentions afterward is weight, or the tendency to proceed downward. He also demonstrates the presence of aqueous vapor in the air by the phenomena of absorption and evaporation. A quotation of his language at this point will give a fair idea of his logic and his style: “In short, garments hung on the surf-beaten shore grow moist, but if spread out in the sun they become dry again. Yet we have not seen how the moisture of the water made its way in, nor how it vanished beneath the heat. The water, then, is scattered into minute parts, which the eyes can in no way behold.” He employs arguments that are in use nowadays in physics to prove the smallness to which matter can be subdivided. The most solid bodies, such as rings upon the fingers and the very stones beneath our feet, are worn away by constant rubbing. “But,” as he goes on to say, “the nature of sight has enviously shut off the view of those portions of the substance which disappear at any one time.”

The arguments which he uses in this connection form an additional proof of the scientific tendency of Lucretius’s mind. In his time the inductive and experimental methods were imperfectly understood and little practiced. He himself does not appear to have attained to them, he was bound by the false philosophical notions of the Greeks; yet often, as here, he traces the cause from various effects with considerable sagacity. He has in several cases, though generally on insufficient evidence, anticipated some of the results of modern research. It is easy to see how his opinions would have been strengthened, and what added breadth and vigor of reasoning he would have gained, if he had stood on our vantage-ground and had known all that we now know. As it is, we feel surprised at finding that he accomplished so much with such imperfect material for his work.

We do not intend to follow the entire development of his theory, but merely to trace his relations to science and the scientific spirit. The rest of the first book and the whole of the second are taken up with a description of the action and properties of the primitive atoms, of which he supposes all things to be composed. Amid some arguments that appear reasonable, he brings forward a striking fallacy. “If,” says he, “matter is infinitely divisible, the greatest and the least, consisting equally of an infinite number of parts, must be equal.” In other words, a mile and an inch are equal, for they each consist of an infinite number of equally small parts. The mathematical imagination among the ancients must have been very little developed, if such an argument passed muster with minds trained to the investigation of abstract truth.

On the other hand, Newton, perhaps the most exact thinker known to scientific history, has expressed opinions on the constitution of matter closely resembling those of Lucretius. The latter asserts that all substance consists of atoms, which are perfectly solid, and therefore incapable of being crushed or torn apart; for that which has no void within itself can not be separated into parts: moreover, they are exceedingly hard, for otherwise they could not form hard bodies like iron; yet, when combined with "much void," they can give rise to soft substances, as water and air. Compare this statement with Sir Isaac Newton's belief, as expressed in the following terms: "It seems probable that God, in the beginning, formed matter in solid, massy, hard, impenetrable, movable particles of such size, figures, and with such other properties, and in such proportion to space, as most conduced to the end for which he formed them; and that these primitive particles, being solid, are incomparably harder than any porous body compounded of them—even so very hard as never to wear, or to break in pieces." If we except the belief in the creative power of God, this quotation gives us Lucretius's atomic theory in a nutshell.

Our author is again in harmony with the latest deductions of physics, when he asserts that the atoms have in themselves no sensible properties, such as color, heat, etc. But the arguments which he uses to establish this proposition are by no means convincing. His treatment of the atomic motions, however, is the most vulnerable point in his system. He supposed all constituted things to be produced by the impact of atoms, which through all eternity were descending, urged on by their own weight. Now, Lucretius had very clear ideas on the subject of gravitation. He knew that, except when in a resisting medium, all bodies fall with equal velocities. Hence, in this everlasting, downward rain, it would be impossible for one atom to approach another and combine with it. To obviate this difficulty, he conceived a slight lateral motion, by which the particles are brought together. He offers no reason for this extraordinary hypothesis, except that no other supposition can explain the formation of things so as to accord with his theory. It is the old story of system first and facts afterward, and shows well the injurious tendency of the a priori method in one who was otherwise well fitted for the pursuit of knowledge.

Passing on to his other teachings, we find him devoting a whole book to the bodily sensations. These, he attempts to show, are produced by corporeal images given off from bodies, and coming into contact with our organs of sense. Thus, he thought that all things were giving off thin pellicles of substance, which, by impinging upon the eye, cause the sensation of sight. This is not unlike Newton's emission hypothesis. His theory of sound also is more purely mechanical than that at present accepted. He supposes this sensation to be caused by the direct passage of particles from the source of sound to the ear, and seems to have had no idea of motion communicated continuously so as to produce waves. His remarks under this general head are often quite correct, and show that he had some capacity for observation.

When treating of the heavenly bodies, he is ordinarily far out of the way. With him the earth is fixed, and the sun and stars revolve about it. With strange perversity, he denies that the orbs of these bodies can be much larger than they appear, no matter at what distance they are placed. On the other hand, in treating this subject he sometimes displays that suspension of judgment which, as opposed to hasty theorizing, is one of the first characteristics of the careful thinker. He himself says: "I assign a number of reasons, one of which must be true; but which among them is true is not for a cautious man to decide."

He next traces the development of man from savagism to civilization; but, though the account is interesting, it has little to do with his views of physical science, and we therefore pass on to the consideration of the remainder of his work, which treats of various natural phenomena, and explains their causes.

He supposes thunder to be produced by the clashing together of clouds, or by the sudden expansion of a volume of air contained in a cloud. This latter action he compares to the bursting of a bladder. Other causes he enumerates, connected with the effects of winds and lightning, whose action on the clouds may produce sound. Lightning, in his view, is struck out like sparks from flint by the friction of the clouds, or it may be caused by the heat generated by the rapid rotation of a hollow cloud.

His views on the cause of water-spouts are similar to those held by many at the present day, namely, that they originate in the vortex of a whirlwind.

His ideas of the nature of clouds are confused, though in one place, at least, he asserts that they are formed by the combination of vapor which is exhaled from the ocean and the earth's surface. The act of raining he ascribes to the compelling force of the winds and the weight of the clouds themselves.

The opinions which he entertains in regard to earthquakes are specially noteworthy, as having been revived of late years by several scientists to explain some, if not all, of the phenomena attendant upon such convulsions of nature. He supposes these to be caused by subterranean downfalls of large masses of rock.

This view has not only been accepted by a number of modern geologists, but also, as Élisée Reclus[1] remarks, has been corroborated by many observations. To this author we commend the reader who desires to know the various reasons for accepting the theory.

The eruption of volcanoes is referred by Lucretius to the expansion of air heated in the cavities of the earth. Modern theorists would rather explain their occurrence by the expansion of steam under great pressure in some underground passage.

Our author goes on with the explanation of many other phenomena. But he is continually led into error by his desire to accommodate the explanation of the effects to suit his theory. As a specimen, we may quote his view of magnetic attraction. According to the Epicurean belief, all substances gave off pellicles or effluvia, which, as before remarked, were supposed to affect the senses. When, then, a magnet and a piece of iron are brought near each other, the effluvia from the former drive away the air between the two bodies, and particles of iron rush to fill the vacuum so caused. Since these particles are very coherent, they draw the rest of the iron after them. The magnet does not attract gold, because that substance is too weighty; wood, on the other hand, is so porous that the atoms of the effluvia pass through it without difficulty. Amid all these absurdities he seems to have had a really philosophic idea of atmospheric pressure. He says: "The surrounding air is continually dashing upon [bodies]; and it drives the iron forward, under such circumstances [as those mentioned before], because the space on one side is empty, and receives [the iron] into itself." He seems also to have had a crude idea of the modern germ theory of disease, and this idea he dwells upon in the closing portion of his work. He describes the means by which disease is spread, and instances the plague at Athens,[2] with a magnificent description of which he concludes his poem.

We have traced such of the principles of the author as seem to bear on the relations of ancient to modern science. We see what effect a false method produced in a man of undoubted genius, endowed with a genuine appreciation of nature and a scientific tendency of mind. Anxious for a rational explanation of every part of the wonderful universe that surrounded him, he was not contented with the slow processes of observation and experiment, but hastened to assign the most probable a priori causes to everything. And thus, whenever he states a physical truth, he appears to have stumbled upon it quite accidentally. It is no reproach to modern men of science that they have been anticipated in their discoveries by a Roman who lived nineteen centuries ago. Rather, it is their glory that, for the vague intuitions of the poet-philosopher, they have substituted the certainty of demonstration; and, by toilsome study in fields which the ancients either neglected or despised, have gained generalizations far surpassing any of his in grandeur. It is not, therefore, for any discoveries that he made, still less for his method of acquiring knowledge, that we give Lucretius a place in the scientific ranks; it is rather for the high qualities of intellect, scientific cast of imagination, and a will that never faltered in the earnest pursuit of truth for its own sake. In every age these are the true characteristics of a man of science.

  1. "The Earth," chapter lxxiv.
  2. Broke out b. c. 430. An accurate account of it is given by Thucydides, from whom Lucretius is thought to have taken his description.