look rather like an unconscious prophecy of the future progress of science than an account of the process of enquiry exhibited in the book.
A few out of many erroneous assertions about physical facts, in regard to some of which the opinions of Lucretius are behind the science even of his own time, may be noticed. Thus, at i. 1052, the existence of the Antipodes is denied. Again, in Book iii. the mind is stated to be a material substance, seated in the centre of the breast, composed of very minute particles, the relative proportions of which determine the characters both of men and animals. Lucretius shows a close and subtle observation of facts that establish the interdependence of mind and body, but no suspicion of that interdependence being connected with the functions of the brain and nervous system. His whole account of the mundus, of the earth at rest in the centre, and of the rolling vault of heaven, with its sun and moon and stars—'trembling fires in the vault'—all no larger than they appear to our eyes, is given without any notion of the inadequacy of his data to bear out his conclusions. The science which satisfied Epicurus was on astronomical and meteorological questions behind that attained by the mathematicians of Alexandria: and thus some of the conclusions enunciated by Virgil in the Georgics are nearer the truth than those accepted by Lucretius. While enlarging on the variety and subtlety in the combinations of his imaginary atoms, he has no adequate idea of the variety and subtlety in the real forces of Nature. His observation of the outward and visible appearances of things is accurate and vivid: there is often great ingenuity as well as a true apprehension of logical conditions in his processes of reasoning both from ideas and from phenomena: yet most of his conclusions as to the facts of Nature, which are not immediately perceptible to the senses, are mere fanciful explanations, indicating, indeed, a lively curiosity, but no real understanding of the true conditions of the enquiry. The root of his error lies in his not feeling how little can be known of the processes and facts of Nature by ordinary observation, without the resources of experiment and of scientific method built upon experiment.
The weak points of this philosophy, the mistaken aim and incomplete method of enquiry, the real ignorance of facts disguised under an appearance of systematic treatment, the unproductiveness of the results for any practical accession to man's power over Nature, are quite obvious to any modern reader, who, without any special study of physical science, cannot help being familiar with information which is now universally diffused, but which was beyond the reach of the most ardent enquirers and original thinkers of antiquity. But the amount of information possessed by different ages, or by different men, is no criterion of their relative intellectual power. The mental force of a strong and adventurous thinker may be recognised struggling even through these mists of error. The weakness of the system, interpreted by Lucretius, is the necessary weakness of the childhood of knowledge. But along with the weakness and the ignorance there are also the keen feeling, the clear eye, and the buoyant fancies of early years,—the germs and the promise of a strong maturity.
The full light in which ancient poetry, history, and mental philosophy can still be read, makes us apt to forget that a great part even of the intellectual life of antiquity has left scarcely any record of itself. Of one aspect of this intellectual life Lucretius is the most complete exponent. The genius of Plato and Aristotle has been estimated, perhaps, as justly in modern as in ancient times. But the great intellectual life of such men as Democritus, Empedocles, or Anaxagoras, escapes our notice in the more familiar studies of classical literature. The work of Lucretius reminds us of the intensity of thought and feeling, the clearness and minuteness of observation, with which the earliest enquiries into Nature were carried on. In some respects the general ignorance of the times enhances our sense of the greatness of individual philosophers. Each new attempt to understand the world was an original act of creative power. The intellectual strength and enthusiasm displayed by the poet himself may be regarded as some measure of the strength of the masters, who filled his mind with affection and astonishment.
The history of the physical science of the ancients cannot, indeed, be regarded as so interesting or important as that of their metaphysical philosophy. And this is so, not only on account of the comparative scantiness of their real acquisitions in the one as compared with the ideas and method which they have contributed to the other, and with the masterpieces which they have added to its literature; but still more on this account, that in physical knowledge new discovery supplants the place of previous error or ignorance, and can be understood without reference to what has been supplanted; whereas the power and meaning of philosophical ideas is unintelligible, apart from the knowledge of their origin and development. The history of physical science in ancient times affords satisfaction to a natural curiosity, but is not an indispensable branch of scientific study. The history of ancient mental philosophy, on the other hand,—the source not only of most of our metaphysical ideas and terms, but of many of the most familiar thoughts and words in daily use,—is the basis of all speculative study. Yet among the various kinds of interest which this poem has for different classes of modern readers this is not to be forgotten, that it enables a student of science to estimate the actual discoveries, and, still more, the prognostications of discovery attained by the irregular methods of early enquiry. The school of philosophy to which Lucretius belonged was distinguished above other schools for the attention which it gave to the facts of Nature. Though he himself makes no claim to original discovery, he yet shows a philosophical grasp of the whole system which he adopted, and a rigorous study of its details. He does not, like Virgil, merely reproduce some general results of ancient physics, to enhance the poetical conception of Nature: as he is not satisfied with those general results about human life and the origin of man, which amused a meditative poet and practical epicurean like Horace. He was a real student both of the plan of Nature and of man's relation to it. Out of the stores of his abundant information the modern reader may best learn not only the errors but also the happy guesses and pregnant suggestions of ancient science.
To the general reader there is another aspect, in which it is interesting to compare these germs of physical knowledge with some tendencies of scientific enquiry in modern times. The questions, vitally affecting the position of man in the world, which are discussed or raised by Lucretius in the course of his argument, are parallel to certain questions which have risen into prominence in connexion with the increasing study of Nature. Most conspicuous among these is the relation of physical enquiry to religious belief. Expressions such as this,
Impia te rationis inire elementa viamque
Indugredi sceleris,
show that scientific enquiry had to encounter the same prejudice in ancient as in modern times. The insufficiency and audacity of human reason were reprobated by the antagonists of Lucretius as they often are in the present day. Ancient religion denounced those who investigated the origin of sun, earth, and sky, as
Immortalia mortali sermone notantes.[402]