The Mechanics of Development.

5. The minds of the supporters of the mechanical theory had still to move along a fifth line in order to solve the riddle of the development of the living individual from the egg, or of the germ to its finished form, the riddle of morphogenesis. They cannot a.s.sume the existence of "the whole"

before the part, or equip it with the idea of the thing as a _spiritus rector_, playing the part of a metaphysical controlling agency. Here as elsewhere they must demonstrate the existence of purely mechanical principles. It is simply from the potential energies inherent in its const.i.tuent parts that the supply of energy must flow, by means of which the germ is able to make use of inorganic material from without, to a.s.similate it and increase its own substance, and, by using it up, to maintain and increase its power of work, to break up the carbonic acid of the atmosphere and to gain the carbon which is so important for its vital functions, to inst.i.tute and organise the innumerable chemico-physical processes by means of which its form is built up. Purely as a consequence of the chemico-physical nature of the germ, of the properties of the substances included in it on the one hand, and of the implicit structure and configuration of its parts, down to the intrinsic specific undulatory rhythm of its molecules, it must follow that its ma.s.s grows exactly as it does, and not otherwise, that it behaves as it does and not otherwise, duplicating itself by division after division, and by intricate changes arranging and rearranging the results of division until the embryo or larva, and finally the complete organism, is formed.

An extraordinary amount of ingenuity has been expended in this connection, in order to avoid here, where perhaps it is most difficult of all, the use of "teleological" principles, and to remain faithful to the orthodox, exclusively mechanical mode of interpretation. To this category belong Darwin's gemmules, Haeckel's plastidules, Nageli's micellae, Weismann's labyrinth of ids, determinants, and biophors within the germ-plasm, and Roux's ingenious hypothesis of the struggle of parts, which is an attempt to apply the Darwinian principle within the organism in order here also to rebut the teleological interpretation by giving a scientific one.(66)

Heredity.

6. With this fifth line of thought a sixth is a.s.sociated and intertwined.

The problem of development is closely bound up with that of "heredity." A developing organism follows the parental type. The acorn in its growth follows the type of the parent oak, repeating all its morphological and physiological characters down to the most intimate detail. And the animal organism adds to this also the whole psychical equipment, the instincts, the capacities of will and consciousness which distinguish its parents.

The problems of the fifth and sixth order are closely inter-related, the sixth problem being in reality the same as the fifth, only in greater complexity.

A step towards the mechanical solution of this problem was indicated in the "preformation theory" advanced by Leibnitz, and elaborated by Bonnet.

According to this theory the developing organism is enclosed in the minutest possible form within the egg, and is thus included in the parental organism, in miniature indeed, but quite complete. Thus the problem of the "development of form" or of "heredity" was, so to speak, ruled out of court; all that was a.s.sumed was continuous growth and self-unfolding.

Opposed to this theory was one of later growth, the theory of epigenesis, which maintained that the organism developed without preformation from the still undifferentiated and h.o.m.ogeneous substance of the egg. The supporters of the first theory considered themselves much more scientific and exact than those of the second. And not without reason. For the theory of epigenesis obviously required mysterious formative principles, and equally mysterious powers of recollection and recapitulation, which impelled the undifferentiated ovum substance into the final form, precisely like that of its ancestors. Nor need the preformationists have greatly feared the reproach, that the parental organism must have been included within the grand-parental, and so on backwards to the first parents in Paradise. For this "Chinese box" encapsulement theory only requires that we should grant the idea of the infinitely little, and that idea is already an integral part of our thinking.

Modern biologists ridicule the preformation hypothesis as altogether too artificial. And undoubtedly it founders on the facts of embryology, which disclose nothing to suggest the unfolding of a pre-existent miniature model, but show us how the egg-cell divides into two, into four, and so on, with continued multiplication followed by varied arrangements and rearrangements of cells-in short, all the complex changes which const.i.tute development. But a preformation in some sense or other there must be;-some peculiar material predisposition of the germ, which, as such, supplies the directing principle for the development, and the sufficient reason for the repet.i.tion of the parental form. This is of such obvious importance from the mechanical point of view that the speculations of to-day tend to move along the old preformationist lines. To these modern preformationists are opposed the modern upholders of epigenesis or gradual differentiation, who attempt to elaborate a mechanical theory of development. And with the contrast between these two schools there is necessarily a.s.sociated the discussion as to the inheritance or non-inheritance of acquired characters.

Darwin's contribution to the problem of the sixth order was his rather vague theory of "Pangenesis." The living organism, according to him, forms in its various organs, parts, and cells exceedingly minute particles of living matter (gemmules), which, "in some way or other," bear within them the special characteristics of the part in which they are produced. These may wander through the organism and meet in the germ-plasm, and then, when a child-organism is produced, they "swarm," so to speak, in it again "in some way or other," and in some fashion control the development. This gemmule-theory was too obviously a _quid pro quo_ to hold its ground for long. Various theories were elaborated, and the world of the invisibly minute was flooded with speculations.

The most subtle of these, on the side of consistent Darwinism, is that of Weismann, a p.r.o.nounced preformation theory which has been increasingly refined and elaborated in the course of years of reflection. According to Weismann, the individual parts and characteristics of the organism are represented in the germ-plasm, not in finished form, but as "determinants"

in a definite system which is itself the directing principle in the building up of the bodily system, and with definite characteristics, which determine the peculiarities of the individual organs and parts, down to scales, hairs, skin-spots, and birth-marks. As the germ-cells have the power of growth, and can increase endlessly by dividing and re-dividing, and as each process of division takes place in such a way that each half (each product of division) maintains the previous system, there arise innumerable germ-cells corresponding to one another, from which, therefore, corresponding bodies must arise (inheritance). It is not in reality the newly developed bodies which give rise to new germ-cells and transfer to them something of their own characters; the germ-cells of the child-organism develop from that of the parent ("immortality" of the germ-cells). Therefore there can be no inheritance of acquired characters, and no modifications of type through external causes; and all variations which appear in a series of generations are due solely to internal variations in the germ-cells, whether brought about by the complication of their system through the fusion of the male and female germ-cells, or through differences in the growth of the individual determinants themselves. The numerous subsidiary theses interwoven in Weismann's theory are entirely coherent, and have been thought out to their conclusions with praiseworthy determination.(67) To the theory as a whole, because of its fundamental conception of preformation, and to its subsidiary hypotheses, piece by piece, there has been energetic opposition on the part of the upholders of the modern mechanical theory of epigenesis. This opposition is most concretely and comprehensively expressed in Haacke's "Gestaltung und Vererbung." The infinitely complex intricacy of Weismann's minute microcosm within the germ-cell, indeed within every id in it, is justly described as a mere duplication, a repet.i.tion in the infinitely little of the essential difficulties to be explained. The complicated processes of developing in the growing and inheriting organism cannot be explained, they say, in terms of processes of the equally complex and likewise developing germ-plasm. The complex, if it is to be explained at all, must be explained by the simple-in this case by the functions of a h.o.m.ogeneous uniform plasm.

At an earlier date Haeckel had made an attempt in this direction in his theory of the "perigenesis of the plastidules." Peculiar states of oscillation and rhythm in the molecules of the germ-substance, handed on to it from the parent organism and transferable to all the a.s.similated matter of the offspring, represent, according to this theory, the principle which impels development to follow a particular course corresponding to the type of the parents. This was a _physical_ way of interpreting the matter. Other investigators have given a _chemical_ expression to their theoretical schemes for explaining heredity.

Haacke declares both these to be unsatisfactory, and replaces them by morphological formative principles. It is the _structure_ of the otherwise h.o.m.ogeneous living matter that explains morphogenesis and inheritance.

Minute "gemmae," h.o.m.ogeneous fundamental particles of living substance, not to be compared to or confused with Darwin's "gemmules," are aggregated in "Gemmaria," whose configuration, stability, symmetrical or asymmetrical structure, and so on, are determined by the relative positions of the gemmae to each other, and these in their turn control the organism and give it a corresponding symmetrical or asymmetrical, a firmly or loosely aggregated structure. The completed organism then forms a system in organic equilibrium, which is constantly exposed to variations and influences due to external causes (St. Hilaire), and to use and disuse of organs (Lamarck). These influences affect the structure of the gemmaria, and as the germ-cells consist of gemmaria, like those of the rest of the organism, the possibility of the transmission of acquired new characters is self-evident. The importance of correlated growth and orthogenesis is explained on a similar basis, and the Darwinian conceptions of the independent variation of individual parts, of the exclusive dominance of utility, of the influence of the struggle for existence in regard to individual selection, and of the omnipotence of natural selection, are energetically denied.

Oscar Hertwig,(68) de Vries, Driesch(69) and others attempt to reconcile the preformationist and the epigenetic standpoints, and "to extract what is good and usable out of both." Hertwig and Driesch, however, can only be mentioned with reservations in this connection.

We cannot better sum up the whole tendency of the construction of mechanical theories on these last lines than in the words of Schwann: "There is within the organism no fundamental force working according to a definite idea; it arises in obedience to the blind laws of necessity."

So much for the different lines followed by the mechanical theories of to-day. An idea of their general tenor can be gained from a series of much quoted general treatises, of which we must mention at least the "cla.s.sics." In Wagner's "Handworterbuch der Physiologie," 1842, Vol. I., Lotze wrote a long introductory article to the whole work, on "Life and Vital Force." It was the challenge of the newer views to the previously vitalistic standpoint, and at the same time it was based on Lotze's general principles and interspersed with philosophical criticism of the concepts of force, cause, effect, law, &c.(70) A similar train of ideas to Lotze's is followed to-day by O. Hertwig, especially in his "Mechanismus und Biologie."(71) Lighter and more elegant was the polemic against vital force, and the outline of a mechanical theory which Du Bois-Reymond prefaced to his great work, "Untersuchungen uber die tierische Electricitat" (1849). It did not go nearly so deep as Lotze's essay, but perhaps for that very reason its phrases and epigrams soon became common property. We may recall how he speaks of vital force as a "general servant for everybody," of the iron atom which remains the same whether it be in the meteorite in cosmic s.p.a.ce, in the wheel of the railway carriage, or in the blood of the thinker, and of a.n.a.lytic mechanics which may be applied even to the problem of personal freedom.

The most comprehensive and detailed elaboration of the mechanical theory of life is to be found in Herbert Spencer's "Principles of Biology."(72) Friedrich Albert Lange's "History of Materialism" is a brilliant plea for mechanical theories,(73) which he afterwards surpa.s.sed and neutralised by his Kantian Criticism. Verworn, too, in his "Physiology"(74) gives a clear example of the way in which the mechanical theory in its most consistent form is sublimed, apparently in the idealism of Kant and Fichte, but in reality in its opposite-the Berkeleyan psychology. A similar outcome is in various ways indicated in the modern trend of things.

CHAPTER IX. CRITICISM OF MECHANICAL THEORIES.

In attempting to define our att.i.tude to the mechanical theory of life, we have first of all to make sure that we have a right to take up a definite position at all. We should have less right, or perhaps none, if this theory of life were really of a purely "biological" nature, built up entirely from the expert knowledge and data which the biologist alone possesses. But the principles, a.s.sumptions, supplementary ideas and modes of expression along all the six lines we have discussed, the style and method according to which the hypothesis is constructed, the mult.i.tude of separate presuppositions with which it works, and indeed everything that helps to build up and knit the biological details into a scientific hypothesis, are the materials of rational synthesis in general, and as such are subject to general as well as to biological criticism. What is there, for instance, in Weismann's ingenious biophor-theory that can be called specifically biological, and not borrowed from other parts of the scientific system?

One advantage, indeed, the biologist always has in this matter, apart from his special knowledge; that is, the technical instinct, the power of scenting out, so to speak, and immediately feeling the importance of the facts pertaining to his own discipline. It is this that gives every specialist the advantage over the layman in dealing with the data of his own subject. This power of instinctively appraising facts, which develops in the course of all special work, can, for instance in hypotheses in the domain of history, transform small details, which to the layman seem trivial, into weighty arguments. Similarly it may be that the success of the mechanical interpretation in regard to isolated processes may make its validity for many other allied processes certain, even though there is no precise proof of this. But we cannot regard this as a final demonstration of the applicability of the mechanical theory, since the same technical instinct in other experts leads them to reject the whole hypothesis.

But here we are met with something surprising. May it not be that while we are impelled on general grounds to contend against the mechanical interpretation of vital phenomena, we are not so impelled on _religious_ grounds? May it not be that the instinct of the religious consciousness is misleading when it impels us-as probably every one will be able to certify from his own experience-to rebel against this mechanisation of life, the mechanical solution of its mysteries? Lotze, the energetic antagonist of "vital force," the founder of the mechanical theory of vital processes, was himself a theist, and was so far from recognising any contradiction between the mechanical point of view and the Christian belief in G.o.d, that he included the former without ceremony in his theistic philosophical speculations. His view has become that of many theologians, and is often expressed in a definition of the boundaries between theology and natural science. According to the idea which was formulated by Lotze, and developed by others along his lines, the matter is quite simple. The interest which religion has in the processes of nature is at once and exclusively to be found in teleology. Are there purposes, plans, and ideas which govern and give meaning to the whole? The interest of natural science is purely in recognising inviolable causality; every phenomenon must have its compelling and sufficient reason in the system of causes preceding it. All that is and happens is absolutely determined by its causes, and nothing, no _causae finales_ for instance, can co-operate with these causes in determining the result. But, as Lotze says, and as we have repeatedly pointed out, causal explanation does not exclude a consideration from the point of view of purpose, and the mechanical interpretation does not do so either. For this is nothing more than the causal explanation itself, only carried to complete consistency and definiteness. Purposes and ideas are not efficient causes but results.

Where, for instance, there is a controlled purposive occurrence, the "purpose" nowhere appears as a factor co-operating with the series of causes, for these follow according to strict law, and the "purpose"

reveals itself at the close of the series, as the result of a closed causal nexus, complete in itself, always provided that the initial links in the chain have been accurately estimated. The same is true of the processes of life. They are the ultimate result, strictly necessary and sufficiently accounted for in terms of mechanical sequence, of a long chain of causes whose initial links imply a definite const.i.tution which could not be further reduced. Whether this ultimate result is merely a result or whether it is also a "purpose" is a question which, as we have seen twice already, it is wholly beyond the power of the causal mode of interpretation to answer. Given that an infinite intelligence in the world wished to realise purposes without inst.i.tuting them as directly accomplished, but by letting them express themselves through a gradual "becoming," the method would be exactly what is shown in the mechanical theory of life, that is, the primitive data and starting-points would have inherent in them a peculiar const.i.tution and a rigidly inexorable orderliness of causal sequence. And Lotze emphasises that it would also be worthier of G.o.d to achieve the greatest by means of the simplest, and to work out the realisation of His eternal purposes according to the strict inevitableness of mechanism, than to attain His ends through the complicated means, the advent.i.tious aids, and all the irregularities implied in the incommensurable activities of a "vital force." ("G.o.d needs no minor G.o.ds.")

To Lotze himself these original data and starting points are the primitive forms of life, which, according to his view, are directly "given," and cannot be referred back to anything else (except to "creation"). But it is obvious that his view can be enlarged and extended so as to refer the derivation of the whole animate world to the original raw materials of the cosmos (energy, matter, or whatsoever they may be), and to the orderly process by which these materials were combined in various configurations to form the chemical elements, the chemical compounds, living proteids, the first cell, and the whole series of higher forms. If this nexus has taken place, it is nothing else than the transformation of the "potential"

into the "actual" through strict causality. And if this actuality proves itself to have claims, because of its own intrinsic worth, to be considered as intelligent "purpose," the whole system of means, including the starting-point, can be recognised as the means to an end, and the original wisdom and the intelligence which ordained the purpose is only glorified the more through the great simplicity, the rational comprehensibility, and the inexorable necessity of the system, which excludes all chance, and therewith all possibility of error.

This extension of Lotze's reconciliation of the mechanical causal with the teleological point of view is impressive and, as far as it goes, also quite convincing. It will never be given up, even if the point of view should change somewhat. And we have already seen that it is quite sufficient as long as we are dealing only with the question of teleology.

But we must ask whether religion will be satisfied with "teleology" alone, or whether this is even the first requirement that it makes in regard to natural phenomena. We have already asked the question and attempted to clear the ground for an answer. Let us try to make it more definite.

Many people will have a certain uneasiness in regard to the Lotzian ideas; they will be unable to rid themselves of a feeling that this way of looking at things is only a _pis aller_ for the religious point of view, and that the fundamental requirements of religious feeling receive very inadequate satisfaction on this method. The world of life which has arisen thus is altogether too rational and transparent. It is calculable and mathematical. It satisfies well enough the need for teleology, and with that the need for a supreme, universally powerful and free intelligence; but it gives neither support nor nourishment to the essential element in religious feeling, through which alone faith becomes in the strict sense religious. Religion, even Christian religion, is, so to speak, a stratified structure, a graduated pyramid, expressing itself, at its second (and undoubtedly higher) level, in our recognition of purpose, the rationality of the world, our own spiritual and personal being and worth, but implying at its basis an inward sense of the mysterious, a joy in that which is incommensurable and unspeakable, which fills us with awe and devotion. And religion at the second stage must not sweep away the essence of the stage below, but must include it, at the same time informing it with new significance. Whoever does not possess his religion in this way will agree with, and will be quite satisfied with the Lotzian standpoint.

But to any one who has experience of the most characteristic element in religion, it will be obvious that there must be a vague but deep-rooted antipathy between religion and the mathematical-mechanical conception of things. Evidence of the truth of this is to be found in the instinctive perceptions and valuations which mark even the nave expressions of the religious consciousness.(75) For it is in full sympathy with a world which is riddled with what is inconceivable and incommensurable, in full sympathy with every evidence of the existence of such an element in the world of nature and mind, and therefore with every proof that the merely mechanical theory has its limits, that it does not suffice, and that its very insufficiency is a proof that the world is and remains in its depths mysterious. Now we have already said that the true sphere for such feeling is not the outer court of nature, but within the realm of the emotional life and of history, and, on the other hand, that even if the attempt to trace life back to the simpler forces of nature were successful, we should still be confronted with the riddle of the sphinx. But any one who would say frankly what he felt would at once be obliged to admit that the religious sense is very strongly stirred by the mystery of vital phenomena, and that in losing this he would lose a domain very dear to him. These sympathies and antipathies are in themselves sufficient to give an interest to the question of the insufficiency of the mechanical view of things.

For it is by no means the case that the mechanical theory, with its premisses and principles, is the interpretation that best fits the facts, and that most naturally arises out of a calm consideration of the animate world. It is an artificial scheme, and astonishing energy has been expended on the attempt to fit it to the actual world, that it may make this orderly and translucent. It certainly yields this service so far, but not without often becoming a kind of strait-jacket, and revealing itself as an artificiality. In so far as the special problems of biology are concerned, we shall afterwards follow our previous method of taking our orientation from those specialists in the subject who, in reaction from the one-sidedness of the mechanical doctrine, have founded the "neo-vitalism" of to-day. Here we are only concerned with the generalities and presuppositions of the theory.

We must dispute even the main justification of the theory, which is sought for in the old maxim of parsimony in the use of principles of explanation (_entia_, and also _principia, praeter necessitatem non esse multiplicanda_), and in Kant's "regulative principle," that science must proceed as if everything could ultimately be explained in terms of mechanism. For surely our task is to try to explain things, not at any cost with the fewest possible principles, but rather with the aid of those principles which appear most correct. If nature is not fundamentally simple, then it is not scientific but unscientific to simplify it theoretically. And the proposition bracketed above has its obvious converse side, that while ent.i.ties and principles must not be multiplied except when it is necessary, on the other hand their number must not be arbitrarily lessened. To proceed according to the fundamental maxims of the mechanistic view can only be wholesome for a time and, so to speak, for paedagogical reasons. To apply them seriously and permanently would be highly injurious, for, by prejudging what is discoverable in nature, it would tend to prevent the calm, objective study of things which asks for nothing more than to see them as they are. It would thus destroy the fineness of our appreciation of what there really is in nature. This is true alike of forcible attempts to reduce the processes of life to mechanical processes, and of the Darwinian doctrine of the universal dominance of utility. Both bear unmistakably the stamp of foregone conclusions, and betray a desire for the simplest, rather than for the most correct principles of interpretation.

There is one point which presses itself on the notice even of outsiders, and is probably realised even more keenly by specialists. The confidence of the supporters of the mechanical theories of earlier days, from Descartes onward, that animals and the bodies of men were machines, mechanical automata, down to the mechanical theories of Lamettrie and Holbach, of _l'homme machine_, and of the _systeme de la nature_, was at least as great as, probably greater than, that of the supporters of the modern theories. Yet how nave and presumptuous seem the crude and wooden theories upon which the mechanical system was formerly built up, and how falsely interpreted seem the physiological and other facts which lent them support, when seen in the light of our modern physiological knowledge.

Vaucanson's or Drozsch's duck-automaton or clockwork-man, with which the mechanical theorists of bygone days amused themselves, would not go far to encourage the physiologist of to-day to pursue his mechanical studies, but would rather throw a vivid light on the impossibility of comparing the living "machine" with machines in the usual sense. For things emphatically do not happen within the living organism in the same way as in the automatic duck, and the more exact the resemblance to the functions of a "real" duck became, the more did the system of means by which the end was attained become unlike vital processes. It is difficult to resist the impression that in another hundred years,-perhaps again from the standpoint of new and definitely accepted mechanical explanations,-people will regard our developmental mechanics, cellular mechanics, and other vital mechanics much in the same way as we now look on Vaucanson's duck.

a.s.sociated or even identical with this is the fact that in proportion as mechanical interpretation advances, the difficulties it has to surmount continually crop up anew. Processes which seem of the simplest kind and the most likely to be capable of purely mechanical explanation, processes such as those of a.s.similation, digestion, respiration, for which it was believed that exact parallels existed in the purely mechanical domain, as, for instance, in the osmotic processes of porous membranes, are seen when closely scrutinised as they occur in the living body to be extremely complex; in fact they have to be transferred "provisionally" from the mechanical to the vital rubric. To this category belong the whole modern development of the cell-theory, which replaces the previously _single_ mechanism in the living body by millions of them, every one of which raises as many problems as the one had done in the days of cruder interpretation. Every individual cell, as it appears to our understanding to-day, is at least as complicated a riddle as the whole organism formerly appeared.

But further: the modern development of biology has emphasised a special problem, which was first formulated by Leibnitz (though it is in ant.i.thesis to his fundamental Monad-theory), and which appears incapable of solution on mechanical lines. Leibnitz declared living beings to be "machines," but machines of a peculiar kind. Even the most complicated machine, in the ordinary sense, consists of a combination of smaller "machines," that is to say, of wheels, systems of levers, &c., of a simpler kind. And these sub-machines may in their turn consist of still simpler ones, and so on. But ultimately a stage is reached when the component parts are h.o.m.ogeneous, and cannot be a.n.a.lysed into simpler machines. It is otherwise with the organism. According to Leibnitz it consists of machines made up of other machines, and so on, into the infinitely little. However far we can proceed in our a.n.a.lysis of the parts, we shall still find that they are syntheses, made up of most ingeniously complex component parts, and this as far as our powers of seeing and distinguishing will carry us. That is to say: organisation is continued on into the infinitely little.

Leibnitz's ill.u.s.tration of the fish-pond is well known. He could have no better corroboration of his theory than the results of modern investigation afford. His doctrine of the continuation of organisation downwards into ever smaller expression is confirmed to a certain extent even by anatomy. By a.n.a.lysing structural organisation down to cells a definite point seemed to have been reached. But it now appears that at that point the problem is only beginning. One organisation is made up of other organisations-cells, protoplasm, nucleus, nucleolus, centrosomes, and so on, according to the power of the microscope; and these structures, instead of explaining the vital functions of growth, development, multiplication by division, and the rest, simply repeat them on a smaller scale, and are thus in their turn living units, the aggregation of which is ill.u.s.trated better by the a.n.a.logy of a social organism than by that of a mechanical structure.

In order to follow the mechanical explanation along the six lines we have previously indicated, we shall, as we have already said, entrust ourselves to the specialists who are on the opposite side. The difficulties and objections which the mechanical theory has to face have forced themselves insistently upon us even in the course of a short sketch such as has just been given, but they will be clearly realised if we approach them from the other side. But, first of all, a word as to the fundamental and, it is alleged, una.s.sailable doctrine on which the theory as a whole is based, the "law of the conservation of energy." The appeal to this, at any rate in the way in which it is usually made, is apt to be so distorted that the case must first be clearly stated before we can get further with the discussion.

The Law of the Conservation of Energy.

Helmholtz's proof established mathematically what Kant had already, by direct insight, advanced as an _a priori_ fundamental axiom: that in any given system the sum of energy can neither increase (impossibility of a _perpetuum mobile_) nor diminish (there is no disappearance of energy, but only transformation into another form). But even the vitalist had no need to deny this proposition. The "energy" which is required for the work of directing, setting agoing, changing and rearranging the chemico-physical processes in the body, and bringing about the effective reactions to stimuli which result in "development," "transmission," "regeneration," and so on-if indeed any energy is required-of course could not come "from within" as a spontaneous increase of the existing sum of energy-that would, indeed, be a magical becoming out of nothing!-but must naturally be thought of as coming "from without." The appeal to the law of the conservation of energy is therefore in itself irrelevant; but it conceals behind it an a.s.sertion of a totally different kind, namely, that in relation to physico-chemical sequences there can be no "without," nothing transcending them-an a.s.sertion which Helmholtz's arguments cannot and were never intended to establish. But before any definite att.i.tude to this newly imported a.s.sertion could be taken up, it would require to be distinctly defined, and that would lead us at once into all the depths of epistemological discussion. Here, therefore, we can only say so much: If this a.s.sertion is accepted it is well to see where it carries us; namely, back to the first-described nave standpoint, which, without critical scruples, quite seriously accepts the world as it appears to it for the reality, and quite seriously speaks of an infinity lying in time behind us-and therefore come to an end-and is not in the least disturbed from its "dogmatic slumber" by this or any of the other great antinomies of our conception of the universe. And it remains, too, for this standpoint to come to terms with the fact that, in voluntary actions, of which we have the most direct knowledge, we have through our will the power of intervention in the physico-chemical nexus of our bodily energies-a fact which implies the existence of a "without," from which interpolations or influences may flow into the physico-chemical system, even if there be none in regard to the domain of "vital" phenomena. And we should require to find out through what parallelistic or abruptly idealistic system the "without" was done away with in this case. For if a transcendental basis, or reverse side, or cause of things, be admitted-even if only in the form of our materialistic popular metaphysics (the "substance" of Haeckel's "world-riddle")-then a "without," from which primarily the cosmic system with its constant sum of matter and energy is explained, is also admitted, and it is difficult to see why it should have exhausted itself in this single effort.

Criticisms of the Mechanistic Theory of Life.

The course of the mechanistic theory of life has been surprisingly similar to that of its complement, the theory of the general evolution of the organic world. The two great doctrines of the schools, Darwinism on the one hand, the mechanical interpretation of life on the other, are both tottering, not because of the criticism of outsiders, but of specialists within the schools themselves. And the interest which religion has in this is the same in both cases: the transcendental nature of things, the mysterious depth of appearance, which these theories denied or obscured, become again apparent. The incommensurableness and mystery of the world, which are, perhaps, even more necessary to the very life of religion than the right to regard it teleologically, rea.s.sert themselves afresh in the all-too-comprehensible and mathematically-formulated world, and re-establish themselves, notwithstanding obstinate and persistent attempts to do away with them. This is perhaps to the advantage of both natural science and religion: to the advantage of religion because it can with difficulty co-exist with the universal dominance of the mathematical way of looking at things; to the advantage of natural science because, in giving up the one-sidedness of the purely quant.i.tative outlook, it does not give up its "foundations," its "right to exist," but only a _pet.i.tio principii_ and a prejudice that compelled it to exploit nature rather than to explain it, and to prescribe its ways rather than to seek them out.