# Popular Science Monthly/Volume 81/August 1912/Modern Thought

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* MODERN THOUGHT
By Dr. EDWARD F. WILLIAMS
CHICAGO, ILL.
WHILE purely metaphysical writings have not ceased to attract attention, it must be admitted that public interest has been drifting away from them and busying itself with inferences drawn from the study of nature and with speculations based upon these inferences. Yet here a philosophy has grown up, taking the form ordinarily of the theories more or less striking which leaders in scientific studies have held concerning the origin and laws of the universe. Some of these theories express very clear and decided opinions concerning man, his origin, capacity and destiny. But all agree that he stands in close relation to the visible, and that he alone of all living creatures can exercise a real and an intelligent control over it.
In a review of the thought of the last century, or century and a half, one is compelled to begin with a recognition of a fact which the majority of scientists, some of them unwillingly, accept, that back of all that appears, ever has appeared, or ever will appear, is thought, the outcome of mind, intelligent, directing, self-controlling mind. It is through the exercise of mental power that the meaning of nature is discerned, that significance is given to facts which penetration into her secrets has revealed. Neither atoms nor their combinations are of the least importance unless there is mind to make use of this combination. When we observe the changes which are constantly occurring in the natural world we can not avoid the question, What has thought to do with them? What influence have these changes had upon thought, what part has thought had in bringing them about?
Passing over for the present scientific theories formed and held in America, in southern or eastern Europe, and confining ourselves to the three great centers of modern European thought, France, Germany and Great Britain, we shall not be far out of the way if we assert that the beginnings of modern scientific theories are found in England or Scotland and have been made by individuals working in isolation with little help and scant encouragement from government, or royal societies, ​or universities: that these discoveries on British soil, like those involved in the theories of Newton, Harvey and Young, were taken up in Paris by members of the Academy of Sciences and through the aid of the government and by means of a wise organization of students of science were tested and their value made known to the world. It is to LaPlace of the Paris Academy of Sciences, more than to any one else, that Newton's theories were made known and were at last universally accepted. Paris up to the middle of the nineteenth century was the most important center of organized scientific study in the world. It was here that the experiments of Lavoisier in chemistry were made, here that Cuvier, Arago and scores of other men introduced into their studies the methods of exact measurements and weights, brought scientific procedure to mathematical precision and stated results in mathematical formulas. It was in Germany, in the universities rather than in the academies, that these results were recorded, and through numerous periodicals given to the world. Germany long has been, and still is, the country of year books in which the history and progress of each special science is carefully traced and preserved for the benefit of the scholar. In France pains were taken with the literary form in which scientific discoveries were published, and a popularity was thereby secured for them unknown either in England or in Germany.
Two factors enter into intellectual progress, the extension or increase of knowledge, and its condensation. Reports of discoveries in any department of learning must be reduced to their lowest terms, or they will not be read, much less studied and made of use. In its accumulations of knowledge the nineteenth century is unsurpassed, but in condensation of knowledge some think it inferior to the time of Pericles in Athens. Nor is it certain, others say, that during the Renaissance, Italy did not surpass anything done in our modern era, and many give the palm to Prance during the sixteenth and seventeenth centuries. But the nineteenth century has no rival in its success in discovering and marking out new and better methods than any previously known, for increasing knowledge. It was in that century that the important conception of the unity of knowledge became prominent. In the opening of the twentieth century the desire to discover truth has not lost in strength, but our students and thinkers are exceedingly careful in the examination of the criteria of truth, for they have learned that not all which seems true, or is proclaimed as true, is true and can be accepted as true. Still men of science are wont to speak of their methods of study as "exact," and to call their discoveries "exact truth." The truths involved in these discoveries are tested by being brought into contact with practical life, that is, tested by experience. In all this thought is present and prominent. It is the thinker in the laboratory, in the factory, in the new industry established as the outcome of years ​of experiment, who is to be considered, the thinker whose aims and works give character to the age.
Attempts have been made from time to time by men who have felt themselves masters of the thought and learning of their era to bring these results together and unify them under some comprehensive term. Thus Herder in his "Ideas for the History of the Human Race" emphasizes Humanity as the proper subject of study, Humanity in the large all-embracing sense. To Hegel it was the Geist, or the spirit of an age which deserves attention. Lotze, a philosopher of great repute not long since deceased, believing that men are living in that sphere of the cosmos of which Humboldt wrote, directed the thought of his time to man as the chief figure of the universe, the microcosmus in the cosmos. Herbert Spencer, without denying the existence of the unknowable or the absolute, testified to his belief in the unity of all things by the prominence he gives in his writings to the social organism. This organism he admits may be, probably is, under the control of an intelligent power but of which we can, he thinks, have no trustworthy knowledge. In these efforts to find some single expression under which all knowledge may be grouped and estimated at its real value, the tendency of the age toward unity is seen. What is desired and sought for is some theory which may be characterized by a single term by means of which whatever is can be explained, or its meaning clearly set forth. Humboldt in the cosmos sought to describe and explain the striking features of the physical world from the standpoint of a philosophical traveler. Hegel wrote as an idealistic philosopher, as a descendant, though not a follower of Kant. Herder and Lotze were, influenced by the poetry and the current philosophy of their time, while men like Du Bois Reymond, denying that they were under the influence of any guiding star, adopted as their motto Ignoramus, Ignorabimus, Dubetemus, Laboremus. Haeckel as a pronounced materialist is still trying to guess the meaning of the riddles of the universe. In his position he is valiantly and ably opposed by the spiritualist, Sir Oliver Lodge.
It is not easy to find a road which will take one through the diversified and often confused thought of a single age, or a race, to say nothing of the thought of all the ages. Here and there events are prominent enough to characterize a century, or several centuries. Such was the case in the history of the Hebrew people, the early centuries of the Christian church, the century in which the power of the Pope culminated, the age of the revival of learning, the era of the reformation, the period of the French revolution, the beginning of the still continuing tendency among the more intelligent nations toward self-government, the most successful example being our own republic. Yet as a thinking age the nineteenth century has no distinguishing title. If it had we might have been spared such philosophies as those of the ​unconscious, or the unknowable, and many others whose life has been short. Still, careful investigation into the leading traits of past centuries often reveals the existence of at least one thinker, sometimes of several thinkers, whose ideas and accomplishments have given character and prominence to his century. Thus we have the century of Augustine, that of Scotus Erigena, that of Anselm, that of Thomas Aquinas, that of Lord Bacon, that of Rousseau and Voltaire, who in a time of comparative quiet really prepared the way for the strife and destruction of the revolution. Perhaps there are men now living, even if we do not recognize them, whose thought and deeds will in the distant future characterize our times.
It has been well said that thought runs from the exact mathematical form to the vaguest religious form, from demonstration to feeling, from knowledge to faith. By this it is not meant that faith does not lay hold of realities, but that its objects are not the objects which awaken and retain the interest of the man of science, or of the lover of exact thought. Philosophy occupies herself with the region which lies between that of science and that of faith. We have therefore three kinds of thought, scientific, philosophical, religious, or as Kant might express it, transcendental. These may be united in a mind sufficiently capacious, as they surely are in the divine mind, but of this union this is not the place to speak.
In Germany from 1800 to 1830, perhaps a little later, the chief interest was in philosophy, as well it might be when such men were living as Fichte, Schelling, Hegel and their illustrious pupils. In France it was in science, of which the results were set forth in books or reports whose literary form was well nigh perfect, when men like Arago, Cuvier and their associates in the Paris Academy of Sciences were in their prime. In England it was the influence of individual thinkers, appearing here and there, often unexpectedly. For a time the writings of Wordsworth, Coleridge, Southey, Shelley and later of Browning and Tennyson affected thought, as in Germany the writings of Schiller, Lessing and Goethe had done. In a certain sense, as Merz remarks, the century began and ended in a ferment of opinion. In England and Scotland Wordsworth, Coleridge and Burns are followed by Byron. In Germany Kant is followed by degenerate materialistic systems of philosophy which he would have abhorred, as well as by some that were idealistic which yet would not have won his approval. It will be observed that the destructive schools of philosophy introduce nothing that is entirely new to the thinking world. Yet the cultivated mind is seriously at work, so that as the century progresses new ideas are formulated and are proving themselves constructive in character. This the words employed indicate, e. g., energy, its conservation or dissipation. The words, individualism, personality recall Lotze with ​his theory of values, while phrases like Natural Selection and the doctrine of evolution recall Darwin and Spencer. Words and phrases alike point to a struggle for condensation of thought in terms so clear and simple that no one can mistake their meaning.
Inasmuch as science has become international and we no longer speak of it as French, English or German, but simply as science, something in which all seekers after truth have a common ownership, a few of those explanations of the universe may now be considered which "exact thought" has given. We may look first of all at the abstract views, four in number, which are ancient in their origin, mathematical in their form and are still ardently defended. These are what have been termed the astronomical view of the world, the atomic view, the kinetic view and the physical view. The latter is the explanation given by those who believe in energy as the underlying and directing cause of movements or changes in the universe.
The astronomical theory rests on the doctrine of gravitation and explains the phenomena of the world in which we live as well as the relation and movements of the heavenly bodies to each other by the assumption of its universal existence. Upon the principle that bodies attract each other directly as their mass, inversely as the square of their distance, Newton enunciated his law of falling bodies. Upon this same principle the tides were explained as well as the revolution of the earth on its own axis and round the sun, the rotation of the heavenly bodies around their axes and around the sun, their motion through space and the velocity of this motion. If gravitation is universally operative on the earth, why should it not be operative everywhere? Through aid of the calculus Newton was able to apply the law of gravitation with the utmost accuracy and by its application lay bare the secrets of the heavenly bodies.
Newton's principles were received more favorably in France than in England. Under the influence of Laplace and the Paris Academy of Sciences, in spite of the protest of a sceptic here and there these principles were, after thorough and somewhat bitter discussion, accepted as true in France, and in no long time in all Europe. On Newton's theory of gravity, the corpuscular explanation of light made its way in scientific circles. Light was believed to be a substance and its laws of reflection and refraction were explained by the law of falling bodies.
The discovery of magnetism in 1791, of the voltaic pile in 1800, and researches into the phenomena of electricity, together with a growing conviction that space is empty and that matter is composed of atoms and requires a void, weakened confidence in the astronomical theory as a full and satisfactory explanation of all the phenomena of the universe. No one denied the facts which Newton had brought forward. No one ventured to assert that gravitation does not act everywhere, or that its ​application does not explain cosmic phenomena, though difficulties even here were suggested, but even if it account for the action of molar objects, i. e., those objects which can be weighed, measured and handled, it does not answer the questions which are put to us by the world of atoms. The study of chemistry and the queries raised by its revelations compelled the defenders of Newton's theories as a sufficient explanation of all phenomena in the heavens and on earth to enter upon a renewed investigation of the basis on which they rest, and to give patient consideration to the phenomena of the atomic world. At length, and because some other action than that of gravity was needed to explain molecular phenomena, the relation of atoms to each other, the phenomena of magnetism and electricity, what is known as the atomic theory was suggested and very generally received, not, however, as setting aside any truths discovered by Newton or involved in the astronomical theory, but as supplementing it and accounting with something like reason for the molar and molecular phenomena which it overlooked or did not recognize as existing.
This atomic theory is not an entirely modern theory. Empedocles of Sicily, who lived in the fifth century before Christ, accepting four primal elements, earth, air, fire and water, explained their modifications and their actions one upon the other, by assuming the existence of two principles, love and hate, attraction and repulsion, which are constantly in operation and which create the forms we behold and account for all the activity in the universe. The atomic theory developed, far more fully than by Empedocles, by Democritus of Abdera of the same century and defended by him with a wealth of learning possessed by no other man of his time gained wide acceptance. In its modern form the theory secured recognition in France and Germany earlier than in England. The exact methods of chemists and mathematicians, first in France then in Germany, led to the belief that matter is not a single piece of something in empty space, but is made up of a multitude of individual and indivisible particles which only partially fill this space, which is filled by that indefinable something which we call ether and which we affirm to be necessary both for sight and hearing.
As chemistry was more earnestly and wisely studied, as the laws of the combination of so-called elemental substances were better understood, men of science became less and less unwilling to admit the inadequacy of Newton's theory of gravitation as an explanation of all phenomena and the more ready to accept a theory which explained, as it seemed to them, the movements in the molecular world, and which, if matter is composed, as was asserted, of atoms, might explain conditions everywhere. Berzelius of Sweden demonstrated the truth of the theory by his wonderful experiments. Dalton's theory of atomic weights was accepted as in harmony with what seemed to be facts. Van't Hoff discovered, so it is believed, laws governing the arrangement of elements ​or atoms in space which are as regular and as important as those assigned by the astronomers to the movements and arrangements of the heavenly bodies. If bodies are formed out of elements that combine with one another on some fixed and definite principle, and not under pressure of the law of gravitation, if this combination is universal, then there must be some law more elemental than that involved in gravity to explain this combination, to account for the phenomena of magnetism and electricity, to explain the disclosures of the microscope in that molecular world which underlies all that the most delicate instruments can render visible. For these and similar reasons the atomic theory of the universe has been proposed. Yet it is recognized as exceedingly complicated and not without need of modification.
But while this theory is held by large numbers of eminent scientists, since 1860 the study of gases has brought about a modification of it and given birth to the kinetic theory of the universe—the old theory of Heraclitus of Ephesus adapted to modern conditions—viz., that all things are in motion. The experiments of Clausius of Zürich, of James Clerk Maxwell of Scotland, and the practical applications of their theories and his own by Joule of Manchester in the study of heat, made it clear that what seems to be the dead pressure of the gases is an apparent rest of particles which are in reality engaged in a constant and law-determined bombardment of each other.
These particles, it was shown, move laterally and with well-nigh incredible speed. It is motion which reveals this long-hidden secret of the gases. It is motion also which accounts for the rigidity of solid bodies. The theory of motion, based on the doctrine of gravity as set forth by Newton and his successors, was the foundation of astronomy. That theory received the support of Huyghens of Holland, of Euler of Berlin and St. Petersburg, the famous mathematician, and was accepted by Young, Count Bumford and Fresnel. Young's undulatory theory of light was made known to the world during the decade from 1791 to 1801. The kinetic theory, the theory of motion everywhere, motion directed, determined and controlled by fixed law, received hesitatingly at first, was steadily opposed by Laplace, but was at last made popular by Arago and Fresnel in France. The doctrine of the polarization of light proved, it is affirmed, by the interference of light waves, contributed to its acceptance. Still opinions even in the Paris Academy were unsettled and confused. Hence the offer by the academy of a prize for an essay which should consider this whole subject, weigh calmly conflicting theories, discover the truth or the falsehood in each one of them, and with all possible thoroughness subject this new theory of motion to the severest tests. At the request of the academy, but against his wishes, Fresnel undertook the investigation. He began his studies with the conviction that this new theory had little foundation upon which to rest. But after careful experiment ​and profound meditation he was convinced of its truth, and gave his reasons for his changed opinions in an essay which received the prize and was read to the academy in 1819, but which for some reason was not published till 1826. The difficulty in explaining transverse vibrations was overcome by showing that polarized rays of light have laterality, and by showing how a stretched string vibrates. The mechanical difference between light and sound was discovered. The tremor which causes sound, it was shown, is in the elastic fluid which carries the movement forward. Without motion there can be neither vision nor hearing. As motion is required to explain the behavior of gases and that fact had been set forth clearly in the experiments of Clausius, Maxwell and Joule, the conclusion did not seem to be far fetched that motion exists everywhere, and must be considered in whatever explanation one attempts to make of physical phenomena. It was also discovered that bodies moving rapidly round an axis, when immersed in water or in any movable medium, cease their rotation and flow forward as other bodies flow in water. In 1857 Helmholtz and Lord Kelvin brought forward the vortex theory to explain cosmic conditions and to account for the formation of the planetary worlds. The studies and experiments of Faraday in electricity and magnetism seemed to favor this new theory of motion. It was shown that the medium which carries light and sound can not possess the ordinary properties of a solid, a liquid or a gas. Hence a demand for a medium in which everything may exist, through the aid of which all movements or vibrations may be conveyed. Careful studies discovered the velocity which particles of hydrogen, for example, obtain, and Faraday pointed out lines of force, afterwards called "tubes of force" by Hertz, along which in a magnetic field, the electric movement passes. These movements were measured mathematically and with such care and accuracy that not only is the course which electricity takes known but its velocity also. But even if electricity be displacement, and its track be accurately discovered and followed, no one pretends to know just what is its innermost nature or denies that future study may entirely change present opinions as to its nature and its laws.
It has been proved, scientists declare, that all forces of matter may be measured and expressed in terms of energy or motion. During the last twenty years the conception has been formed that light is an electric or a magnetic phenomenon. Luminous waves are short rapidly moving waves and difference in color is caused by difference in length and frequency. But what is most important in this theory of motion is that it is not necessary, as in the gravitation theory or the atomic theory, to believe in the theory of action at a distance. Bodies move because other bodies press upon them. We see and hear because some sort of motion brings the ether into connection with eye and ear. The fact of gravity is not denied. Nor is it denied that Newton's ​discoveries in reference to its action in the physical world explain the motions and relations of the heavenly bodies, but it is affirmed confidently that the theory of universal motion or the kinetic theory removes more difficulties in the explanation of the phenomena of the universe than either the astronomical or the atomic theory. In passing, it may be mentioned that this theory of universal motion was taught not only by Heraclitus, but by Anaxagoras of Athens, who saw that with his well-nigh innumerable germs he could not solve the problems of the universe apart from motion, and therefore introduced into his system of philosophy, the nous, or intelligence, to give the first push to matter and impart to it the movement which he believed to be universal and without which life could not exist.
The fourth of the abstract theories employed to explain the universe is the physical theory or the theory of energy. By this theory we understand that whatever is or has come to be has been caused by the force or energy there is in matter. The astronomical theory fails to account satisfactorily for molecular activity and chemical affinity: the kinetic theory is set aside because it is based on dualism or the existence of matter and ether. What is true in these theories is preserved and the difficulties found in the application of each one of them are avoided by the use of the general term energy, a term under which, according to Young, all that is known in science may be expressed. Energy or force is that something in nature which can do work and be stated in terms of horse power. We speak of latent energy, of energy created by friction, by the fall of water, by steam, and, although we are unable to define it, we describe it as something everywhere present and able, when properly harnessed or directed, to do a certain amount of work.
While refusing to speak of energy as a property of matter and denying that it is matter in any true sense of the word, it is affirmed that its amount in the material world can neither be increased nor diminished, that while from a heated object a certain portion of heat departs in cooling, a fact which is described as entropy, the sum total of energy, whether in the form of heat or of some other force, remains the same. This truth is set forth by Helmholtz as the conservation of force, a doctrine which, while admitting that a particular form of energy may be changed into another form, affirms that the energy itself is neither destroyed nor diminished by the transformations through which it may pass. Energy is valueless unless capable of transformation. It is good for nothing till it is made usable. Hence the study of energy has been more constantly directed toward discovering methods by means of which its power may be employed for the welfare of mankind, than toward ascertaining its nature. We know that energy may be changed in form, that it now appears as heat, now as light, now as electricity, now as magnetism. Nor are these the only ​forms it assumes. Having taken pains to conserve energy or to obtain it, the practical question is how to use it?
That energy is everywhere present, underlies all things, was affirmed by Young, Rumford, Black, Müller, Mohr, Liebig, J. B. Mayer, Joule, Carnot, Sir William Thomson, or Lord Kelvin. It was through their efforts chiefly that the theory gained acceptance. It began to attract notice during the first third of the century, although its acceptance even now is by no means universal. Faraday, Mohr and not a few others believed in the existence of something indestructible, connected with matter, yet independent of it, but Helmholtz and his school explain everything mechanically. Heat, for example, is a product of motion. Other natural processes explain other natural manifestations. This theory was brought forward and defended in great part by the Scotch school to which belong the illustrious names of the Thomsons, James and William, Rankine, Clerk Maxwell, P. G. Tait and Balfour Stewart. Working alone, Clausius, of Zürich, reached substantially the same results. Maxwell studied the energy of the electric magnetic field, Joule the energy of the electric current, Watt measured heat. The idea of the unity of all chemical combinations was suggested by Arrhenius, of Sweden, in 1886, who showed how to decompose chemical solutions by the use of the galvanic current. Without saying anything more of this physical theory which presupposes the universal existence of energy as a force in matter, if not a constituent of it, as something which can neither be created nor destroyed by human agencies, though it may, through its power of convertibility into various forms of power, be made extremely useful, we simply add that energy may be so accurately measured by the aid of mathematics that before it is called forth from its hiding place we can ascertain exactly what amount of work it will do. Merz says that this theory has been useful to science in at least four ways.
It has brought out clearer definitions of terms.
It has caused a revision and recasting of physical and chemical knowledge.
It has criticized existing theories from a new point of view.
From this new point of view fresh departures in the study of science have been taken.
What energy is we do not know. It appears as intensity and power to do work. Is it a substance, material in its nature? What need then of ether to carry the undulations which produce sound or vision? Whatever the answer to these enquiries and many others which might be raised, energy seems to be a regulative and a directive rather than a constructive principle. Energy is found everywhere, but it nowhere appears as creative, save in bringing particles of matter together in new forms, or passing itself from one form of existence to another without growing less in amount.
​From this brief review of the abstract or mathematical theories which have been proposed to explain the universe, it appears that while no one can deny the existence of gravity wherever there is matter, or of molecular activity or of motion, or of energy, it is certain that no one of them fully explains the mysteries of the universe. We feel the need of something more, some force or principle, some intelligence underlying all that we can see or discover as existing by the aid of the most powerful instruments, not only to direct and control forces already acting in and upon matter, but to create them and set them in motion.
Passing from these abstract explanations of the origin and nature of the universe and the consideration of their influence upon thought, four other theories, which may be called concrete from the fact that they rest on that which is visible and tangible, the morphological, the genetic, the vitalistic and the psycho-physical, require our attention. These theories are descriptive in their character and are based upon studies in the field rather than in the laboratory or the museum. Abstract science has been of immense advantage to the world of industry, and its methods of investigation will not soon be given up, but the progress made in the descriptive sciences has been very great and not without influence upon mind and life, or, as Merz is fond of saying, upon thought. The conception of energy and descent has helped to break down old distinctions and to establish on a firmer foundation the conception of unity in nature.
Morphology seeks to study objects as a whole rather than in detail, and to study these as they are in nature, before they suffer from changes wrought by the hands of men. The morphologist wants to know things as they are, and why they are. He recognizes the differences in the forms which substance assumes and in the structure of bodies. He considers their relation to each other and to their environment, the effect of climate and of time. But it is the object as a whole rather than any part of it in which he is interested. Such a method of study can not fail to be popular. It appeals to the people at large. Its descriptions can be easily understood and appreciated. Such men as Humboldt, Linnæus, Daubenton, Buffon and Cuvier have been among its distinguished advocates. Natural objects, it will be remembered, may be spoken of as cosmical, molar or molecular. Cosmical or heavenly bodies are magnitudes of immense size in space; molar objects are the objects we can see and handle here on the earth; molecular objects are the objects which are too small for our vision or touch to discover. Cosmical bodies are infinitely large, molecular infinitely small. If all bodies are similar in their composition, as the discoveries through the spectroscope seem to indicate, then a description of the nature of molar objects may be applied to those which are cosmic or molecular.
In the study of nature from a morphological point of view there is need of wide travel. Humboldt in his "Cosmos" has given us the re ​suits of investigations in portions of the world not often visited, and thus has made contributions of inestimable value to science. The study of animals in zoological gardens, if not in their native haunts, and of marine life by sea-going expeditions, or in extensive experimental stations by the seashore, as in Naples, Plymouth, England, or Woods Hole, Mass., has given a new impulse to the study of zoology and biology. The study of forms, especially those that are living, has been of great advantage to the physician also. From the days of Galen till the present time efforts have been made to apply the knowledge of physical laws to bodily healing. Galvanism, electricity, the nature and effect of different foods, the study of animal heat, have been made use of by the physician.
It is to Goethe that we are indebted for the word morphology, which describes his ideas as to the metamorphosis of plants. He saw, even if indistinctly, the unity of plant and animal life and the possible unity of all departments of nature. Merz says:
In the perpetual variety of change the morphological view tries to define those recurring forms or types which present themselves again and again, towards which all changes seem to revert, thus bringing some order into what would otherwise be disorder and confusion. . . . The object of morphology as distinct from that of classification is the attempt to describe, and if possible to comprehend and explain the relative similarity as well as the graduated differences of form and structure which natural objects present to our gaze.
Natural objects can best be studied where nature presents them, under conditions which enable one to see them as they really exist in nature. But the study of nature, as a whole, is often best carried on by a study of its departments. Haüy creates for us in his mastery of the forms of crystals, and of the laws of crystallization, the science of crystallography. It is but a step from crystals to minerals and fossils, thence to plant and animal life. It is not surprising that, following hints from various sources and from his own studies, Theodore Schwann, having established the cellular theory of life, should assert, as he did in 1840, the essential identity of animal and vegetable structure. Since then his special department of study has made vast strides and ere long the science of biology may embrace everything in nature that relates even remotely to life.
Cuvier, the comparative anatomist, while cherishing large views, yet believed in types, in the fixity of species, and explained the changes produced in the world of animal life, the world of fossils, of plants and minerals, by sudden convulsions or catastrophes, by means of which old types of life are destroyed and new ones introduced. In this theory he was opposed by Etienne St. Hilaire, who explained the changes observable in the different departments of nature as the gradual outcome of the forces of nature. In this view he had the sympathy of Goethe.
Morphology without the microscope to assist in its study would have ​made little progress. At the beginning of the last century it was in a backward condition. Improvements in the microscope and in the knowledge of its use, the studies of such men as Amici of Modena, Lister in England, the botanists Hugo von Mohl and Nägeli, of Stokes, Lord Rayleigh and Helmholtz, and the skill of Professor Ernst Abbe, of Jena, who has at his back the celebrated firm of Carl Zeiss, have rendered an exact study of cell life or formation of the tissues of all the processes and conditions of life possible and of value. But if tbe study of geology morphologically has produced men like Lyell, if in botany we have the great names of the Jussieus and De Candolle, in zoology, of Daubenton and Cuvier, more and more clearly has it been seen that nature is after all a unit in her processes. In the new field of astrophysics in which so much use is made of the spectroscope there is hardly a science known which is not employed in its development.
Yet the morphological study of nature alone could not long be satisfying. The progress made in the study of biology, the publication of Darwin's "Origin of Species" and Herbert Spencer's suggestion of the "physiological unit," called attention away from the forms of natural objects, from their study as individuals or collectively, or in relation to each other, from their distribution in various parts of the earth, to the changes wrought in them through the lapse of time, or by water, fire or convulsions of nature, to the processes of their formation or growth. Thus their genesis becomes of even greater interest than their form or their distribution. Indeed even the morphologist feels that his method of interpreting nature would be more satisfactory if he were fully acquainted with the methods which nature employs in the introduction and support of life.
This theory, the second of those we are now considering, is known as the genetic theory—and so called from its dealing with life. This theory assumes that all things are in motion and are developing along many lines, yet after some real order, if not after a fixed and definite plan. The word evolution, so generally used in England to indicate this process, is not universally employed in France or Germany. Herbert Spencer has the credit and the responsibility of introducing the word evolution into English-speaking scientific circles and also for using the word genesis to set forth a purely mechanical conception of the universe.
What we desire to know and seek to know is, How have things come to be, what they are and what is their history in time? Leibniz in his tract "Protogaea," published in 1749 called attention to the part fire and water have had, as indicated by visible proofs of their action, in forming the surface of the earth. He suggested a thorough study of many localities in order that general and satisfactory conclusions might be reached. Kant, influenced as he admits by the theories of Thomas Wright, of Durham, as to the formation of the planetary system, ​proposed a theory of the formation of the universe which was afterwards developed into that well-known nebular hypothesis which till within a few years has been almost universally accepted as a reasonable explanation of the genesis of the stellar world. This theory was strengthened by the study of paleontology in England, and of embryology in Germany. During the first half of the century it was thought by many that life repeats itself, comes and goes in well-defined circles, but this hypothesis was displaced in the second half of the century by a belief in the gradual development of all natural forces toward a certain end. Hence the introduction of the word evolution.
Hutton's opposition to the catastrophic theory in geology prepared the way for Lyell in England who was unwilling to accept the genetic theory without modification. Nor was he content to remain a morphologist. "The Vestiges of Creation," published in 1840, and written by Robert Chambers, of Edinburgh, favored the genetic theory and applied it to the cosmic molar and molecular phenomena. The book, valuable for its suggestions and for the discussions to which it gave rise, met with decided opposition in many circles on the ground of its materialistic views and its tendency to explain nature without any reference to the supernatural. For a similar reason the opinions of many German scientists were unacceptable in Great Britain.
Yet in spite of the weight which the names of Humboldt, Cuvier and Richard Owen carried, it became evident, about the middle of the nineteenth century, that the morphological theory alone would not satisfy the scientific world. Doubts began to be cherished as to the fixity and permanence of species. There was opposition to the catastrophic theories in geology. Sir Charles Lyell in his "Principles of Geology" suggests orderly development, though without breaking with the older theories. Herbert Spencer in his writings in the early fifties sees more clearly than most others the necessity of some such theory as that which was afterwards known as the theory of evolution, or the gradual development of all forms and all life out of a simple original substance. As early as 1759 C. T. Wulff, as a result of his studies on cellular structure and growth, had come to the conclusion that growth is by additions and gave the world his theory of epigenesis. His influence dates from the year 1812 and was made effective through the work of Schleiden, Schwann, Mohl and Pander, who led the way in the study of that scientific embryology of which Pander is accounted the founder. Through these studies and those of Haeckel, which came later, the essential identity of the cell in structure substance and growth in the vegetable and animal world, was established.
As Herbert Spencer had prepared the English mind for the views of Darwin, so Haeckel prepared the way for their favorable consideration in Germany and on the continent. The work of Lamarck and of Von Baer, of Königsberg and St. Petersburg, was also of importance. But ​"The Origin of Species" with its principle of natural selection, its preservation of useful qualities, the influence of environment and heredity, gave the genetic theory strong support. The views presented by its illustrious author were set forth with such clearness and defended with such wealth of illustration as to make their rejection a matter of great difficulty. Even those who were most hostile recognized their importance as well as their revolutionary character. It was evident to nearly every scientific man that henceforth the world could not be explained upon morphological theories alone, and that some such principle as that of natural selection must be presupposed in order to explain the facts which in almost every department of scientific research were daily coming to light. Natural selection has been defined as "that process in life, automatic in its nature and action by which in the struggle for existence useful differences are preserved and those which are not useful are destroyed." It is under the operation of this principle Spencer believed, and sought to show, that species are formed and the various manifestations of life accounted for. Those who accepted Mr. Spencer's theories in full, with few exceptions, accounted for the origin and evolution of the universe on purely mechanical principles.
But the questions as to life itself, its nature and its origin, were not on this evolutionary theory fully answered. Granting that the lowest forms of life are connected with the cell, that life is manifested in its structure and through its growth, even on the assumption that matter and energy only exist, the question can not be pushed aside. Whence is the energy which brings life into matter, organizes it and imparts to it the power or ability under the laws of evolution to create, perfect and continue at pleasure, the forms in which it chooses to appear? Logically the genetic theory must explain the origin and continuance of life on mechanical principles alone. A theory in sharp contrast to the genetic or evolutionary theory, which for many minds reduces life to a mechanical process, is what Mr. Merz calls the vitalistic theory. This theory is becoming more and more prominent with the increasing interest in the study of biology. What life is, what is its origin, what are its processes, are questions to which as yet completely satisfactory answers have not been returned. Bichot (1771-1802) defined life as the "totality of functions which resist death," a definition which gives little information as to the nature of life, or its origin. Claude Bernard (1813-78) wrote "life is the struggle of living forces against the non-living." Since the publication of Darwin's book on "The Origin of Species," or more exactly since 1866, a tendency is to be noted which seeks to establish parallelisms between processes in organic and inorganic bodies. Lavoisier was one of the first to study life from a chemical point of view, and to explain respiration, nutrition and the generation of animal heat as a form of combustion. In ​1783 he and Laplace reported the results of their investigations on the subject of life to the Paris Academy of Sciences, but had little to say about the nature of life itself. In 1839 the British Association requested Liebig to study the subject of biology, as it then existed, and report at a subsequent meeting all that was known about it. The report was thorough, valuable and gave great satisfaction, but shed no light on the origin and nature of life. Though a vitalist, Liebig gave less attention to the defence of this belief than to the applications of the principles of chemistry to economics, especially as related to agriculture. Here his efforts were epoch-making. John Müller, of Berlin, and the Weber brothers, of Leipzig, investigated the physical and mechanical processes of life, so far as they could trace them by careful experiment in the laboratory. Du Bois Beymond and Helmholtz were trained by Müller and were among his most distinguished pupils.
It was while seeking answers to questions which investigations as to the origin and nature of life were constantly presenting that Helmholtz and Meyer, in entire independence of each other, discovered the principle of the conservation of force or energy. In 1847 Helmholtz proved, as he thought beyond any reasonable doubt, that living forces are manifestations of a certain quantity of power to do work. The outcome of these studies and the publication of theories based upon them brought about a change, in Germany especially, in the opinions hitherto held as to the nature of the vital force or vital principle. Not a few were content to reduce life to a mechanical process and to deny any distinction between life and matter. Others sought to discover the life process and to make its development clearer by many different theories. The "potential energy" of Helmholtz, the cell formation theory of Schwann, set forth in 1839, and the theory of Max Verworn, of Jena, that life consists in the "metabolism of proteids" do not require the supposition of any principle or force apart from matter itself to account for life in any of the forms in which it has appeared. And yet these theories do not deny the possibility of the existence of a life principle. Neither does acceptance of the "physiological unit," as suggested by Mr. Herbert Spencer, prevent us from believing that life may be something quite different from this unit and independent of it even if it manifest itself in and through it. Accurately as these life processes, as they are termed, have been traced by the most capable experimenters in the world, the product of these experiments, however exactly it imitate that of nature differs from it in toto. The laboratory product may contain the same elements, and so far as can be seen, arranged in the same proportion, and yet be entirely unlike the product of nature. No chemist has yet learned how to arrange atoms of matter in a living organism and adapt that organism to an environment in any such way as to compete with nature or indeed to give to the product of the laboratory anything worthy of being called life.
​Familiar as one may become with the processes of organization, science has not yet been able to develop life out of what appears to be dead matter. Nor has it yet been proved that life is ever spontaneously developed from dead matter. Something more than mechanical processes, or than the action of matter itself, is required for the production of life even in its simplest and most primitive form. It may come through the cell. The cell itself may be merely a bit of protoplasm. This protoplasm may be either a germ of life or of the body. One thing seems certain; life proceeds from life and is never produced by mechanical processes, however constant these may be after life has once appeared, or however necessary they may be after life has begun its career in matter.
As has been said, the study of biology is fascinating. It is likely to become more fascinating with renewed efforts to attack the problem of life in its secret fastnesses. There will always be some students of biology who will be content to assume the existence of life either as something which may reasonably be taken for granted, or as furnishing a problem which at present can not be solved. But there will be others who will feel that biology must remain an incomplete science so long as the origin and nature of life are unknown. Its study as yet is in the era of beginnings and, in spite of its apparently insoluble problems, is full of promise. For the problems of the science are interesting and worthy an attempted solution, even if it be found advisable to put aside all thought of a solution of the mystery of life itself.
The fourth of the concrete theories of the origin and nature of the universe is called by Merz the psychophysical theory. It presupposes the study of mind and matter as found in man, in their relation to one another. In this study we may proceed from within by introspection or speculatively, or we may proceed from without objectively, obtaining our knowledge of mind from what it does, as shown in history, science, art, language, as Herder suggested should be done.
In the study of mind introspectively, or as it reveals itself in connection with the human machine of which it makes constant and necessary use, such men have been prominent as Cabanis, G. T. Fechner, the leaders of the Naturphilosophie school of Germany, Schelling, Hegel and others, the Weber Brothers, of Leipzig, Du Bois Beymond, Herbart, the philosopher who rejected physiology altogether and insisted upon the study of the mind as a unit by itself, Thomas Young, as shown by his theory of colors, Charles Bell, who discovered the difference between the anterior and posterior roots of the nerves of the spine and did not a little toward pointing out the difference in their functions, and John Müller with his "specific energies" which have long been taken for granted in all physiological reasoning as to the nature of sense perception.
Helmholtz, too, has contributed not a little to the solution of the ​problem as to the relation of body and mind in his works on hearing and seeing and on vision and music. Lotze, who has the credit of having banished the idea of vital force from the study of biology, has given especial attention to the study of the methods or rules of the psychophysical machine. But the most prominent and successful investigator in this special department of mental and physical study is Professor Wundt, of Leipzig. It is said of him that he combines in the methods he follows the truth found in Lotze's medical psychology and Helmholtz's physiology of hearing and seeing with valuable additions of his own. He approaches the study of mind from the side of physiology, but is careful to take into consideration the whole problem of mentality and thus avoid theories founded on the study of only a part of it. The older metaphysical psychologists explained "the unity and unified totality of all inner and mental phenomena" by assuming the existence of an independent entity, "the soul, the person, the self," at the beginning of their discussions. This modern psychology is unwilling to do. The unity of the inner life and its unified totality is a clearly defined problem. This problem Professor Wundt has sought to solve. The question he puts to himself is, "Wherein consists the unity of consciousness, wherein is the totality of all mental life, individual and collective?" It will thus be seen that he and his school are leaving no difficulty untouched, and if the results of their studies are not universally accepted as satisfactory it will not be from any lack of thoroughness on the part of those who have made them.
Objectively, the study of mind psychophysically may be made a basis for the study of language. Or from the study of language one may form some opinion as to the nature and origin of mind. The problems of language are many and difficult of solution. How did language originate? How has it been developed? What does its use indicate? Broca in 1861 located the organ of speech in the center of the brain and by his writings laid the foundation of the science of phonetics, but was unable to overcome the well-nigh universal conviction that we can not account for the beginning of speech or of its development upon a merely mechanical and material basis. Speech implies thought, and thought has not been proved to be an attribute of matter or a product of mechanics. Wundt has not failed to study the problem of mental life objectively as well as introspectively. He has created the science of psychophysics. He has originated the theory of the parallelism of physical and psychophysical phenomena. As easily the first in this department of study, it is to his laboratory and to the men he has trained that students who are awaiting the solution of the difficulties connected with the psychophysical problem are turning for light. Wundt uses the word epiphenomena, which may be discontinuous, even if life itself is continuous, to explain various mental manifestations. But even here in the effort to explain centralization ​and externalization, or the expansion and growth of mind, it would seem almost as if the existence of mind were assumed. At any rate, its existence is not absolutely denied or made identical with matter.
There are scientists who think of mind as they think of matter, and therefore study its operations as if it were the product of physical forces alone. They are not surprised at the conclusions of Cabanis that thought is a product of the brain as organized matter. These conclusions seem to them the logical outcome of Locke's theory of knowledge and of the philosophy taught by the Frenchmen Abbé Condillac and Helvetius. To them there seems to be no good reason why phrenology should not be able to locate the different powers of the brain, as Gall and Spurzheim tried to do at the beginning of the last century, even if no attempt were made to account for the existence of that something called mind which makes use of the brain.
However close we admit the relations to be between mind and matter, however fully we may believe in the influence of the physical upon the mental machine in man, it is well-nigh impossible to escape the conviction that mind and matter are diverse in their nature, that even if mind makes use of matter in its operations and is aided by it so that mind and matter may properly be studied together as a new science, they are not thereby made one and the same thing. There are many who still look upon physiology and psychology as different sciences, and while recognizing their close relationship and welcoming the results of studies and experiments in the border land between the two, they still feel as if there were a science of mind which demands other experiments and studies than those which physiology is able to furnish. Nevertheless, it is certain that in all future studies of mental philosophy the physical nature of man will be taken into account.
From this brief review of theories concerning the universe, its origin and meaning, each of which has been prominent in its turn, each of which indicates a different point of view on the part of its defenders, and each of which has in it a great deal of truth, it is clear that no one of them can now be accepted as completely satisfactory or as covering all the problems which meet us in trying to explain the universe. Taken together, they disclose and give a reason for many of the processes of nature, but they do not explain them all. Indeed, with every new discovery new vistas open, new questions arise, new difficulties are to be met. We may, therefore, content ourselves by accepting that as true which is proved to be true by all the theories. The fact of gravitation is undeniable, even if the astronomical theory is no longer received as adequate. Although no one has ever yet seen an atom, sound reasoning seems to require us to admit the existence of atoms and justifies us in appealing to mathematics to prescribe the laws of an atomic world. Nor can we deny the evidences of universal motion, or that the kinetic theory has a good basis upon which to stand. Equally evident is it ​that force, or energy, energy that can be measured, harnessed, made to do work, exists in matter, and that no satisfactory account of nature can be given which overlooks or neglects it. In these abstract theories we proceed from small beginnings and build up our theories upon conclusions which seem to be true. The great names connected with them are Newton, Lagrange, Fresnel and Helmholtz. In the concrete theories objects are found ready made. We take them as they are and seek to describe them, and give a reason for their distribution and for their existence. Hence the theory which occupies itself with forms, or the morphological theory. Nor is it less a matter of interest to know how these forms have originated, out of what materials and under what conditions. Hence the genetic theory, which is supported by an array of names the scientific world delights to honor. With the study of biology, or life, it is natural that there should be a vitalistic theory, and that in process of time the student should discover a border land between mind and matter subject in part to physical, in part to mental laws. So we have the psychophysical theory of the universe, and the deep and growing interest in the study of its problems. Yet however true each of these theories is, and there is truth in them all, it is certain that as science enlarges her borders, opens new fields of knowledge, these theories will be given up, or be modified to such an extent as to be virtually new, that the study of nature and her processes will continue to the end of time and that whatever advantages the man of science may have one thousand or ten thousand years hence, the problems then demanding solution will be neither less numerous nor less difficult than those which confront him to-day.
Yet these studies are of great value, not only for the practical benefit they bring to the world, but for the influence they have on those who pursue them. They teach men to be tolerant, for the fields to be traversed are so wide, the subjects considered are so varied and complex, and are cultivated with such diverse aims, that one can not be surprised at the different conclusions to which investigators, equally in earnest and equally competent, arrive. In a scientific mind dogmatism has no place. Love for old truth does not prevent hospitality toward that which seems to be new. Scientific studies are fitted by their very nature to produce enlargement of mind, clearness of vision and devotion to the search after truth. The man of science is not only far better prepared for his studies to-day by the mental attitude he is compelled to assume in beginning his special work than ever before; the equipment at his disposal is more complete and better adapted to his wants than his predecessors have enjoyed. Indeed, he is in this respect the heir of all the ages. It is his own fault if he is irreverent toward old truth, inhospitable toward that which is new, or lacking in devotion to search after that truth with which nature is full and is waiting to reveal.