The story is told of Dante that in one of his peregrinations through Italy he stopped at a certain convent, moved either by the religion of the place or by some other feeling, and was there questioned by the monks concerning what he came to seek. At first the poet did not reply, but stood silently contemplating the columns and arches of the cloister. Again they asked him what he desired; and then slowly turning his head and looking at the friars, he answered, "Peace!" The anecdote is altogether too significant to escape suspicion; yet as The Divine Comedy is supposed to contain symbolically the history of the human spirit in its upward growth and striving, so this fable of the divine poet may be held to sum up in a single word the aim and desire of the spirit's endless quest. So clearly is the object of our inner search this "peace" which Dante is said to have sought, and so close has the spirit come again and again to attaining this goal, that it should seem as if some warring principle within ourselves turned us back ever when the hoped-for consummation was just within reach. As Vaughan says in his quaint way:

It is possible, I believe, to view the ceaseless intellectual fluctuations of mankind backward and forward as the varying fortunes of the contest between these two hostile members of our being,—between the deep-lying principle that impels us to seek rest and the principle that drags us back into the region of change and motion and forever forbids us to acquiesce in what is found. And I believe further that the moral disposition of a nation or of an individual may be best characterised by the predominance of the one or the other of these two elements. We may find a people, such as the ancient Hindus, in whom the longing after peace was so intense as to make insignificant every other concern of life, and among whom the aim of saint and philosopher alike was to close the eyes upon the theatre of this world's shifting scenes and to look only upon that changeless vision of

The spectacle of division and mutation became to them at last a mere phantasmagoria, like the morning mists that melt away beneath the upspringing day-star.

Again, we may find a race, like the Greeks, in whom the imperturbable stillness of the Orient and the restless activity of the Occident meet together in intimate union and produce that peculiar repose in action, that unity in variety, which we call harmony or beauty and which is the special field of art. But if this harmonious union was a source of the artistic sense among the Greeks, their logicians, like logicians everywhere, were not content until the divergent tendencies were drawn out to the extreme; and nowhere is the conflict between the two principles more vividly displayed than in that battle between the followers of Xenophanes, who sought to adapt the world of change to their haunting desire for peace by denying motion altogether, and the disciples of Heraclitus, who saw only motion and mutation in all things and nowhere rest. "All things flow and nothing abides," said the Ephesian, and looked upon man in the midst of the universe as upon one who stands in the current of a ceaselessly gliding river. The brood of Sophists, carrying this law into human consciousness, disclaimed the possibility of truth altogether; and it is no wonder that Plato, while avoiding the other extreme of motionless pantheism, regarded the sophistic acceptance of this law of universal flux as the last irreconcilable enemy of philosophy and morality alike. "The war over this point is indeed no trivial matter and many are concerned therein," said he, not without bitterness.

It is, when rightly considered, this same question that lends dramatic unity and human value to the long debate of the mediÆval schoolmen. Their dispute may be regarded from more than one point of view,—as a struggle of the reason against the bondage of authority, as an attempt to lay bare the foundation of philosophy, as a contest between science and mysticism; but above all it seems to me a long conflict in words between these two warring members within us. The desire of infinite peace was the impulse, I think, which drove on the realists to that "abyss of pantheism," from the brink of which the vision of most men recoils as from the horror of shoreless vacuity. In this way Erigena, the greatest of realists, spoke of God as that which neither acts nor is acted upon, neither loves nor is loved; and then, as if frightened by these blank words, avowed that God though he does not love is in a way Love itself, defining love as the finis quietaque statio of the natural motion of all things that move. On the other hand it was the impulse toward unresting activity which led the nominalists to deny reality to the stationary ideas of genera and species, and to fix the mind upon the shifting combinations of individual objects. In this direction lay the labour of accurate observation and experimental classification, and it is with prefect justice that HaurÉau, the historian of scholastic philosophy, closes his chapter on William of Occam, the last of the schoolmen, with these words: "It is then in truth on this soil so well prepared by the prince of the nominalists that Francis Bacon founded his eternal monument,"—and that monument is the scientific method as we see it developed in the nineteenth century.

The justification of scholastic philosophy, as I understand it, was the hope of finding in the dictates of pure reason an immovable resting-place for the human spirit; the recoil from the abyss of pantheism and absolute quietism was the work of the nominalists who in William of Occam finally won the day; and with him scholastic philosophy brought an end to its own activity. But a greater champion than William was needed to wipe away what seems to the world the cobwebs of mediÆval logomachy. Kant's Critique of Pure Reason accomplished what the nominalistic schoolmen failed to achieve: it showed the impossibility of establishing by means of logic the dogma of God or any absolute conception of the universe. Henceforth the real support of metaphysics was taken away, and the study fell more and more into disrepute as the nineteenth century waxed old. Not many men to-day look to the pure reason for aid in attaining the consummation of faith. That consummation, if it be derived at all from external aid, must come henceforth by way of the imagination and of the moral sense. We say with Kant: "Two things fill the mind with ever-new and increasing admiration and reverence, the oftener and the more persistently they are reflected on: the starry heaven above me, and the moral law within me."

But neither the imagination nor the conscience alone, any more than reason, can create faith. They may prepare the soil for the growth of that perfect flower of joy, but they cannot plant the seed or give the increase; for they, both the imagination and the conscience, are concerned in the end with the light of this life, and faith looks for guidance to a different and rarer illumination. Faith is a power of itself; fidem rem esse, non scientiam, non opinionem vel imaginationem, said Zwingle. It is that faculty of the will, mysterious in its source and inexplicable in its operation, which turns the desire of a man away from contemplating the fitful changes of the world toward an ideal, an empty dream it may be, or a shadow, or a mere name, of peace in absolute changelessness. Reason and logic may have no words to express the object of this desire, but experience is rich with the influence of such an aspiration on human character. To the saints it was that peace of God which passeth all understanding; to the mystics it was figured as the raptures of a celestial love, as the yearning for that

To the ignorant it was the unquestioning trust in those who seemed to them endowed with a grace beyond their untutored comprehension.

Even if the imagination or the conscience could lift us to this blissful height, they would avail us little to-day; for we have put away the imagination as one of the pleasant but unfruitful play-things of youth, and the conscience in this age of humanitarian pity has become less than ever a sense of man's responsibility to the supermundane powers and more than ever a feeling of brotherhood among men. Of faith, speaking generally, the past century had no recking, for it turned deliberately to observe and study the phenomena of change. We call that time, which is still our own time, the age of reason, but scarcely with justice. The Middle Ages, despite the obscurantism of the Church, had far better claim to that title. One needs but to turn the pages of the doctors, even before the day of Abelard who is supposed first to have been the champion of reason against authority, to see how profound was their conviction that in reason might be discovered a justification of the faith they held. And indeed Abelard is styled the champion of reason because only with him do men begin to perceive the inability of reason to establish faith. Better we should call ours an age of observation, for never before have men given themselves with such complete abandon to observing and recording systematically. By long and intent observation of the phenomenal world the eye has discovered a seeming order in disorder, the shifting visions of time have assumed a specious regularity which we call law, and the mind has made for itself a home on this earth which to the wise of old seemed but a house of bondage.

From this wealth of observation and record the modern age, and especially the century just past, has developed two fields of intellectual activity to such an extent as almost to claim the creation of them. Gradually through accumulated observation the nineteenth century came to look on human affairs in a new light; like everything else they were seen to be subject to the Heraclitean ebb and flow; and history was written from a new point of view. We learned to regard eras of the past as subject each to its peculiar passions and ambitions, and this taught us to throw ourselves back into their life with a kind of sympathy never before known. We did not judge them by an immutable code, but by reference to time and place. Nor is this all. Within the small arc of our observation we observed a certain regularity of change similar to the changes due to growth in an individual, and this we called the law of progress. History was then no longer a mere chronicle of events or, if philosophical, the portrayal and judgment of characters from a fixed point of view; it became at its best the systematic examination of the causes of progress and development. And naturally this attention to change and motion, this historic sense, was extended to every other branch of human interest: in religion it taught Christians to accept the Bible as the history of revelation instead of something complete from the beginning; in literature it taught us to portray the development of character or the influence of environment on character rather than the interplay of fixed passions; in art it created impressionism or the endeavour to reproduce what the individual sees at the moment instead of a rationalised picture; in criticism it introduced what Sainte-Beuve, the master of the movement, sought to write, a history of the human spirit.

But history, like Cronos of old, possessed a strange power of devouring its own offspring. Gradually, from the habit of regarding human affairs in a state of flux and more particularly from the growth of the idea of progress, the past lost its hold over men. It became a matter of curiosity but not of authority, and history as it was understood in Renan's day has in ours almost ceased to be written. Science on the other hand is the observation of phenomena regarded chiefly in the relation of space—for it is correct, I believe, to assert that the laws of energy may be reduced to this point—and as such is not subject to this devouring act of time. It frankly discards the past and as frankly dwells in the present. It is not my purpose, indeed it would be quite superfluous, to reckon up the immense acquisitions of the scientific method in the past century: they are the theme of schoolboys and savants alike, the pride and wonder of our civilisation. Nor need I dwell on the new philosophy which sprang up from the union of the historic and the scientific sense and still subsists. Not the system of Hegel or Schopenhauer or of any other professor of metaphysics is the true philosophy of the age; these are but echoes of a past civilisation, voices and prÆterea nil. Evolution is the living guide of our thought, assigning to the region of the unknowable the conceptions of unity and perfect rest, and building up its theories on the visible experience of motion and change and development. It has reduced the universal flux of Heraclitus to a scientific system and assimilated it to our inner growth; it has become as essentially a factor of our attitude toward the natural world as Newton's laws of gravitation.

But if our thoughts are directed almost wholly to the sphere of motion, yet this does not mean that the longing after quietude and peace has passed entirely from the mind of man; the thirst of the human heart is too deep for that. Only the world has learned to look for peace in another direction. In place of that faith which would deny valid reality to changing forms, we have taught ourselves to find a certain order in disorder, which we call law,—whether it be the law of progress or the law of energy,—and on the stability of this law we are willing to stake our desired tranquillity.

In this way, through what may be called the offspring begotten on the historic sense by science, the mind has turned its regard into the future and seemed to discern there a continuation of the same law of progress which it saw working in the past. Hence have arisen the manifold dreams and visions of socialism, altruism, humanitarianism, and all the other isms that would fix the hope of mankind upon some coming perfectibility of human life, and that like Prometheus in the play have implanted blind hopes in the hearts of men. It is indeed one of the most curious instances of the recrudescence of ideas to see the mediÆval visions of a city of golden streets and eternal bliss in another existence brought down to the future of this world itself. What to the mystic of that age was to come suddenly, with the twinkling of an eye, when we are changed and have put away mortal things, when the angel of the Apocalypse has sworn that time shall be no longer,—all this, the heavenly city of joy and endless content, is now to be the natural outcome here in this world of causes working in time. The theory is beautiful in itself and might satisfy the hunger of the heart, even though its main hope concerns only generations to come, were it not for a lingering and fatal suspicion that progress does not involve increased capability of happiness to the individual, and that somehow the race does not move toward content. Physical comfort has perhaps become more widely distributed, but of the placid joy of life the recent years have known singularly little; we need but turn over the pages of the more representative poets and prose writers of the past sixty years to discover how deep is the unrest of our souls. The higher literature has come to be chiefly the "blank misgivings of a creature moving about in worlds not realised"; and missing the note of deeper peace we sigh at times even for

Alas, those who would find a resting-place for the spirit in the relations of man to man seem not to reckon that the very essence—if such a term may be used of so contingent a nature—that the very essence of this world's life is motion and change and contention, and that Peace spreads her wings in another and purer atmosphere. One might suppose that a single glance into the heart would show how vain are such aspirations, and how utterly dreary and illusory is every conceived ideal of progress and socialism because each and all are based on an inherent contradiction. He who waits for peace until the course of events has become stable is like the silly peasant by the river side, watching and waiting while the current flows forever and will ever flow.

Not less vain is the hope of those who would find in the laws of science a permanent abiding place—perhaps one should say was rather than is, for the avowed gospel of science which was to usurp the office of olden-time religious faith is already like the precedent historic sense, itself becoming a thing of the past. Yet the much discussed war between science and religion is none the less real because to-day the din of battle has ceased. It does not depend on criticism of the Mosaic story of creation by the one, nor on hostility to progress offered by the other. These things were only signs of a deeper and more radical difference: religion is the voice of faith uttering in symbols of the imagination its distrust of the world as a scene of deception and unreality, whereas science is the attempt to discover fixed laws in the midst of this very world of change. If to-day the strife between the two seems reconciled, this only means that faith has grown dimmer and that science has learned the futility of its more dogmatic assumptions.[10]

The very growth of science is in fact a gradual recognition of motion as the basis of phenomena and an increasing comprehension of what may be called the laws of motion. When motion was regarded as simple and regular, it seemed possible to explain phenomena by correspondingly simple and regular laws; but when each primary motion was seen to be the resultant of an infinite series of motions the question became in like manner infinitely complex, or in other words insoluble. But to be clear we must consider the matter more in detail.

From the days of the old Greek Heraclitus, who built up his theory of the world on the axiom of eternal flux and change, the Doctrine of Motion as a distinct enunciation has lingered on in the world well-nigh unnoticed and buried from sight in the bulk of suppositions and guesses that have made up the passing systems of philosophy. Now and then some lonely thinker took up the doctrine, but only to let it drop back into obscurity; until during the great burst of scientific enquiry in the fifteenth and sixteenth centuries it assumed new significance and began to grow. From that time to this its progress in acceptance as the basis of phenomena may be regarded as a measure of scientific advance.

By a strange fatality Kant, who had been so efficient as an iconoclast in metaphysics, was perhaps with his nebular hypothesis, followed later by the work of Goethe on animal and plant variations, the one most largely responsible for the new hope that in science at last was to be found an answer to the riddle of existence which had baffled the search of pure reason. The achievement of Kant both destructive and constructive is well known, if vaguely understood, by the world at large; but it is not so well known that a contemporary of Kant did precisely for science what the sage of KÖnigsberg accomplished in metaphysics. In the very decade in which The Critique of Pure Reason saw the light, Lagrange, a scholar of France, published a work which carried the analytic method, or the method of motion, to its farthest limit. In this work, the MÉcanique Analytique, Lagrange develops an equation from which it can be proved conclusively that to explain any group of phenomena measured by energy an infinite number of hypotheses may be employed. So, for instance, if we establish any one theory which will sufficiently account for the known phenomena of light, such as reflection, refraction, polarisation, etc., there will yet remain an infinite number of other hypotheses equally capable of explaining the same group of phenomena. Or to use the words of PoincarÉ: "If then we can give one complete mechanical explanation of a phenomenon, there will also be possible an infinite number of others which will account equally well for all the particulars revealed by experiment." That is to say, no experimentum crucis can be imagined which will reveal the truth or error of any given theory. This restriction on the finality of our knowledge is borne out in all physical reasoning,—and I venture also to say in the other sciences; thus in optics we can perform no experiment which will establish as finally true the theory that light is caused by the motion of corpuscles of matter emitted from a luminous body, or that it is due to vibrations propagated through a medium by a wave motion, or that it is generated by certain disturbances in the electrical state of bodies. Each of these hypotheses has its advantages and disadvantages; and in our choice we merely adopt that theory which explains the greater number of phenomena in the simplest way.

If any one should here ask: Granted that from phenomena expressed in terms of energy no ultimate law can be educed, yet may not some other view of phenomena lead to other results? We answer that no other view is possible. Not that the system of the universe, if we may use such an expression, is necessarily constructed on what we call energy, but that our minds can conceive it only in terms of energy. An analysis of the concepts which enter into the idea of energy must make it evident that in our understanding of nature we cannot go beyond this point.

There is an agreement among philosophers and scientists that the concept of space is not derived from external experience, but is inherently intuitive. As stated by Kant:

The concept of space therefore makes possible the intuition of external phenomena; but these phenomena to be realised must appeal to one of our senses, and this connecting link between the outer world and our consciousness is the concept which we call time. Quoting again from Kant:

It follows, then, that our simplest possible expression for phenomena will be in terms of space and time, and that beyond this the human mind cannot go.

Turning here from metaphysical to scientific language, we speak of space and time as the fundamental units from which we deduce the laws of the external world. The fact that space appeals to us only through time furnishes us with our concept or unit of motion, which is the ratio of space to time. The external phenomena so revealed to us we call the manifestations of mass or energy, thus providing ourselves with a second unit. It must be observed, however, that mass or energy is not a new concept, but bears precisely the same relation to motion as Kant's Ding-an-sich bears to space and time: it is the unknowable cause of motion—or more properly speaking it is the ability residing in an object to change the motion of another object and is measured by the degree of change it can produce. And I say mass or energy, advisedly, for the two are merely different names or different views of the same thing; we cannot conceive of matter without energy or of energy without matter. Our choice between the two depends solely on the simplicity and convenience with which deductions may be made from one or the other. From a physical standpoint the concept energy is rather the simpler, but mathematically our deductions flow more readily from the concept mass.

If then our explanations of phenomena must ultimately involve the two units of motion and of energy or mass, and if it can be demonstrated that on this basis we may account for any group of phenomena in an infinite number of ways, what shall we say but that the attempt to attain any resting-place for the mind in the laws of nature is, and must always be, futile? Further than this, any given law is itself only an approximate explanation of phenomena, and must be continually modified as we add to our experimental knowledge. In all cases a law must be considered valid only within the limits of the sensitiveness of the instruments by which we get our measurements. With more delicate instruments variations will be observed that must be expressed by additional terms in the formula. Thus we maintain that the law of gravitation is true only within the range of our observation; it does not apply to masses of molecular dimensions. Another formula, the well-known law of the pressure of gases, can be shown by experiment to be merely an approximation, because the variations in it are not of a dimension negligible in comparison with the sensibility of our instruments. As the pressure increases the error in the formular equation becomes constantly greater. To remedy this a second approximation, which is still inadequate, has been added to the equation by Van der Waals; yet greater accuracy will require the addition of other terms; and a complete demonstration would demand an infinite series of approximations.

The meaning of all this is quite plain: there is no reach of the human intellect which can bridge the gap between motion and rest. Our senses are adapted to a world of universal flux which is, so far as we can determine, subject to no absolute law but the law of probabilities. He who attempts to circumscribe the ebb and flow of circumstance within the bounds of our spiritual needs, he who attempts to find peace in any formula of science or in any promise of historic progress, is like one who labours on the old and vain problem of squaring the circle:

The desire of peace, as the world has known it in past times, signified always a turning away from the flotsam and jetsam of time and an attempt to fix the mind on absolute rest and unity,—the desire of peace has been the aspiration of faith. And because the object of faith cannot be seen by the eyes of the body or expressed in terms of the understanding, a firm grasp of the will has been necessary to keep the desire of the heart from falling back into the visible, tangible things of change and motion. For this reason, when the will is relaxed, doubts spring up and men give themselves wholly to the transient intoxication of the senses. Yet blessed are they that believe and have not seen. It was the peculiar quest of the nineteenth century to discover fixed laws and an unshaken abiding place for the mind in the very kingdom of unrest; we have sought to chain the waves of the sea with the winds.

And how does all this affect one who stands apart, striving in his own small way to live in the serene contemplation of the universe? I cannot doubt that there are some in the world to-day who look back over the long past and watch the toiling of the human race toward peace as a traveller in the Alps may with a telescope follow the mountain-climbers in their slow ascent through the snows of Mont Blanc; or again they watch our labours and painstaking in the valley of the senses and wonder at our grotesque industry; or look upon the striving of men to build a city for the soul amid the uncertainties of this life, as men look at the play of children who build castles and domes in the sands of the seashore and cry out when the advancing waves wash all their hopes away. I think there are some such men in the world to-day who are absorbed in the fellowship of the wise men of the East, and of the no less wise Plato, with whom they would retort upon the accusing advocates of the present: "Do you think that a spirit full of lofty thoughts, and privileged to contemplate all time and all existence, can possibly attach any great importance to this life?" They live in the world of action, but are not of it. They pass each other at rare intervals on the thoroughfares of life and know each other by a secret sign, and smile to each other and go on their way comforted and in better hope.

FOOTNOTES

THE END.