comte, auguste - the positive philosophy vol II

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thus a greater number of cases known, but each case is much better understood by their approximation. This would not be the case, and the problem would be embarrassed instead of simplified, if there were not a fundamental resemblance among the whole series, accompanied by gradual modifications, always regulated in their course: and this is the reason why the comparative method is appropriate to biology alone, of all the sciences, except, as we shall see hereafter, in social physics.

Complete and spontaneous as this harmony really is, no philosopher can contemplate without admiration the eminent art by which the human mind has been aided to convert into a potent means what appeared at first to be a formidable difficulty. I know no stronger evidence of the force of human reason than such a transformation affords. And in this case, as in every other in which primordial scientific powers are concerned, it is the work of the whole race, gradually developed in the course of ages, and not the original product of any isolated mind,— however some moderns may be asserted to be the creators of comparative biology. Between the primitive use that Aristotle made of this method in the easiest cases,—as in comparing the structure of Man’s upper and lower limbs,—to the most profound and abstract approximations of existing biology we find a very extensive series of intermediate states, constantly progressive, among which history can point out individually only labours which prove what had been the advance in the spirit of the comparative art at the corresponding period, as manifested by its larger and more effectual application. It is evident that the comparative method of biologists was no more the invention of an individual than the experimental method of the physicists. There are five principal heads under which biological comparisons are to be classed.

1.Comparison between the different parts of the same organism.

2.Comparison between the sexes.

3.Comparison between the various phases presented by the whole of the development.

4.Comparison between the different races or varieties of each spe-

cies.

5.Lastly, and pre-eminently, Comparison between all the organisms of the biological hierarchy.

It must be understood that the organism is always to be supposed in a normal state. When the laws of that state are fully established, we may pass on to pathological comparison, which will extend the scope of those laws: but we are not yet advanced enough in our knowledge of normal

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conditions to undertake anything beyond. Moreover, though comparative pathology would be a necessary application of biological science, it cannot form a part of that science, but rather belongs to the future medical science, of which it must form the basis.—Again, biological comparison can take place only between the organisms, and not between them and their medium. When such comparison comes to be instituted, it will be, not as biological science, but as a matter of natural history.

The spirit of biological comparison is the same under all forms. It consists in regarding all cases as radically analogous in respect to the proposed investigation, and in representing their differences as simple modifications of an abstract type; so that secondary differences may be connected with the primary according to uniform laws; these laws constituting the biological philosophy by which each determinate case is to be explained. If the question is anatomical, Man, in his adult and normal state is taken for the fundamental unity, and all other organizations as successive simplifications, descending from the primitive type, whose essential features will be found in the remotest cases stripped of all complication. If the question is physiological, we seek the fundamental identity of the chief phenomenon which characterizes function proposed, amidst the graduated modifications of the series of comparative cases, till we find it isolated, or nearly so, in the simplest case of all; and thence we may trace it back again, clothed in successive complications of secondary qualities. Thus, the theory of analogous existences, which has been offered as a recent innovation, is only the necessary principle of the comparative method, under a new name. It is evident that this method must be of surpassing value when philosophically applied: and also that, delicate as it is, and requiring extreme discrimination and care in its estimate and use, it may be easily converted into a hindrance and embarrassment, by giving occasion to vicious speculations on analogies which are only apparent.

Of the five classes specified above, three only are so marked as to require a notice here: the comparison between the different parts of the same organism; between the different phases of each development; and between the distinct terms of the great hierarchy of living bodies. The method of comparison began with the first of these. Looking no further than Man, no philosophical mind can help being struck by the remarkable resemblance that his different chief parts bear to each other in many respects,—both as to structure and function. First, all the tissues, all the apparatus, in as far as they are organized and living, offer those funda-

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mental characteristics which are inherent in the very ideas of organization and life, and to which the lowest organisms are reduced. But, in a more special view, the analogy of the organs becomes more and more marked as that of the functions is so; and the converse; and this often leads to luminous comparisons, anatomical and physiological, passing from the one to the other, alternately. This original and simple method of comparison is by no means driven out by newer processes. It was thus, for instance, that Bichat, whose subject was Man only, and adult Man, discovered the fundamental analogy between the mucous and the cutaneous systems, which has yielded so much advantage to both biology and pathology. And again, with all M. de Blainville’s mastery of the principle of the comparative method, we cannot doubt the sufficiency of the analysis of the human organism to establish the resemblance he exhibited between the skull and the other elements of the vertebral column.

A new order of resources presents itself when we compare the different phases of the same organism. Its chief value is in its offering, on a small scale, and, as it were, under one aspect, the whole series of the most marked organisms of the biological hierarchy; for it is obvious that the primitive state Of the highest organism must present the essential characters of the complete state of the lowest; and thus successively,— without, however, compelling us to find the counterpart of every inferior term in the superior organism. Such an analysis of ages unquestionably offers the property of realizing in an individual, that successive complication of organs and functions which characterizes the biological hierarchy, and which, in this homogeneous and compact form, constitutes a special and singular order of luminous comparisons. Useful through all degrees of the scale, it is evidently most so in the case of the highest type, the adult Man, as the interval from the origin to the utmost complexity is in that case the greatest. It is valuable chiefly in the visible ascendant period of life; for we know very little of the foetal period; and the declining stage, which is in fact only a gradual death, presents little scientific interest: for, if there are many ways of living, there is only one natural way of dying. The rational analysis of death, however, has its own importance, constituting a sort of general corollary, convenient for the verification of the whole body of biological laws.

The popular notion of comparative biology is that it consists wholly of the last of the methods I have pointed out: and this shows how preeminent it is over the others; the popular exaggeration however being mischievous by concealing the origin of the art. The peculiarity of this

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largest application consists n its being founded on a very protracted comparison of a very extensive series of analogous cases, in which the modification proceeds by almost insensible graduated declension. The two more restricted methods could not offer a series of cases extensive enough to establish, without confirmation, the nature and value of the comparative method, though, that point once fixed, they may then come into unquestionable use. As for the value of the largest application, it demonstrates itself. There is clearly no structure or function whose analysis may not be perfected by an examination of what all organisms offer in common with regard to that structure and function, and by the simplification effected by the stripping away of all accessory characteristics, till the quality sought is found alone, from whence the process of reconstruction can begin. It may even be fairly said that no anatomical arrangement, and no physiological phenomenon, can be really understood till the abstract notion of its principal element is thus reached, by successively attaching to it all secondary ideas, in the rational order prescribed by their greater or less persistence in the organic series. Such a method seems to me to offer, in biology, a philosophical character very like mathematical analysis genuinely applied; when it presents, as we have seen, in every indefinite series of analogous cases, the essential part which is common to all, and which was before hidden under the secondary specialities of each separate case. It cannot be doubted that the comparative art of biologists will produce an equivalent result, up to a certain point; and especially, by the rational consideration of the organic hierarchy.

This great consideration was at first established only in regard to anatomy; but it is yet more necessary in physiology, and not less applicable, except from the difficulty of that kind of observation. In regard to physiological problems particularly, it should be remarked that not only all animal organisms, but the vegetable also, should be included in the comparison. Many important phenomena, and among others those of organic life, properly so called, cannot be analysed without an inclusion of the vegetable form of them. There we see them in their simplest and most marked condition, for it is by the great act of vegetable assimilation that brute matter passes really into the organized state, all ulterior transformations by means of the animal organization being much less marked. And thus, the laws of nutrition, which are of the highest importance, are best disclosed by the vegetable organism. The method is unquestionably applicable to all organs and all acts, without any excep-

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tion; but its scientific value diminishes as it is applied to the higher apparatus and functions of the superior organisms, because these are restricted in proportion to their complexity and superiority. This is eminently the case with the highest intellectual and moral functions which below Man disappear almost entirely or, at least, almost cease to be recognizable below the first classes of the mammals. We cannot but feel it to be an perfection in the comparative method that it serves us least where we are most in need of all our resources. but it would be unphilosophical to deprive ourselves, even in this case, of the light which is cast upon the analysis of Man as moral, by the study of the intellectual and affective qualities of the superior animals, and of all others which present such attributes, however imperfect our management of the comparison may yet be. And we may observe that the comparative method finds a partial equivalent in the rational analysis of ages,—thus rendered more clear, extensive, and complete,—for the disadvantages which belong to the same stage of the biological hierarchy.

Thus I have presented the principal philosophical characters of the comparative method. It being the aim of biological study to ascertain the general laws of organic existence, it is plain that no course of inquiry could be more favourable than that which exhibits organic cases as radically analogous, and deducible from each other.

This study of our means of exploration has shown that our resources do increase with the complexity of our subject. The two first methods— of Observation and Experiment—we have seen to acquire a large extension in the case of this science: while the third, before almost imperceptible becomes, by the nature of the phenomena, well-nigh unbounded in its scope. We have next to examine the true rational position of Biology in the hierarchy of the fundamental sciences; that is, its relation to those that precede it, and to the one which follows it, in order to ascertain what kind and degree of speculative perfection it admits of, and what preliminary training is best adapted to its systematic cultivation. By this inquiry we shall see why we are justified in assigning to it a place between chemistry and social science.

Of the relation of Biology to social science, I need say little here, as I shall have to speak of it at length in the next volume. My task will then be to separate them, rather than to establish their connection, which it is the tendency of our time to exaggerate, through the spontaneous development of natural philosophy. None but purely metaphysical philosophers would at this day persist in classing the theory of the human mind

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and of society as anterior to the anatomical and physiological study of individual man. We may therefore regard this point as sufficiently settled for the present, and pass on to the relation of Biology to inorganic philosophy.

It is to chemistry that Biology is, by its nature, most directly and completely subordinated. In analyzing the phenomenon of life, we saw that the fundamental acts which, by their perpetuity, characterize that state, consist of a series of compositions and decompositions; and they are therefore of a chemical nature. Though in the most imperfect organisms, vital reactions are widely separated from common chemical effects, it is not the less true that all the functions of the proper organic life are necessarily controlled by those fundamental laws of composition and decomposition which constitute the subject of chemical science. If we could conceive throughout the whole scale the same separation of the organic from the animal life that we see in vegetables alone, the vital motion would offer only chemical conceptions, except the essential circumstances which distinguish such an order of molecular reactions. The general source of these important differences is, in my opinion, to be looked for in the result of each chemical conflict not depending only on the simple composition of the bodies between which it takes place, but being modified by their proper organization; that is, by their anatomical structure. Chemistry must clearly furnish the starting-point of every rational theory of nutrition, secretion, and, in short, all the functions of the vegetative life, considered separately; each of which is controlled by the influence of chemical laws, except for the special modifications belonging to organic conditions. If we now bring in again the consideration, discarded for the moment, of the animal life, we see that it could in no way alter this fundamental subordination, though it must greatly complicate its actual application: for we have seen that the animal life, notwithstanding its vast importance, can never be regarded in biology otherwise than as destined to extend and perfect the organic life, whose general nature it cannot change. Such an intervention modifies, anew and largely, the chemical laws of the purely organic functions, so as to render the effect very difficult to foresee; but not the less do these laws continue to control the aggregate of the phenomena. If, for instance, a change in the nervous condition of a superior organism disturbs a given secretion, as to its energy or even its nature, we cannot conceive that such an alteration can be of a random kind: such modifications, irregular as they may appear, are still submitted to the chemical laws of the

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fundamental organic phenomenon, which permit certain variations, but interdict many more. Thus, no complication produced by animal life can withdraw the organic functions from their subordination to the laws of composition and decomposition. This relation is so important, that no scientific theory could be conceived of in biology without it; since, in its absence, the most fundamental phenomena might be conceived of as susceptible of arbitrary variations, which would not admit of any true law. When we hear, at this day, on the subject of azote, such a doctrine as that the organism has the power of spontaneously creating certain elementary substances, we perceive how indispensable it still is to insist directly on those principles which alone can restrain the spirit of aberration.

Besides this direct subordination of biology to chemistry, there are relations of method between them. Observation and experimentation being much more perfect in chemistry they serve as an admirable training for biological inquiry. Again, a special property of chemistry is its developing the art of scientific nomenclature; and it is in chemistry that biologists must study this important part of the positive method, though it cannot, from the complexity of their science, be of so much scientific value as in chemistry. It is on the model of the chemical nomenclature that those systematic denominations have been laid down by which biologists have classified the most simple anatomical arrangements, certain well-defined pathological states, and the most general degrees of the animal hierarchy: it is by a continued pursuit of the same method that further improvements will be effected.

We thus see why biology takes its place next after chemistry, and why chemical inquiries constitute a natural transition from the inorganic to the organic philosophy.

The subordination of biology to Physics follows from its relation to Chemistry: but there are also direct reasons, relating both to doctrine and method, why it should be so.

As to doctrine,—it is clear that the general laws of one or more branches of Physics must be applied in the analysis of any physiological phenomenon. This application is necessary in the examination of the medium, in the first place; and the analysis of the medium is required to be very exact, on account of the strong effect of its variations on phenomena so easily modified as those of the organism. And next, the organism itself is no less dependent on those laws, relating as they do to weight, heat, electricity, etc. It is obvious that if biology is related to

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chemistry through the organic life, it is related to physics by the animal life—the most special and noble of the sensations, those of sight and bearing, requiring for the starting-point of their investigation an application of optics and acoustics. The same remark holds good in regard to the theory of utterance, and the study of animal heat and the electric properties of the organism. It remains to be wished that the biologists would study and apply these laws themselves, instead of committing the task to physicists: but they have hitherto followed too much the example of the physicists, who, as we have seen, have committed the application of mathematical analysis in their own science to the geometers, whereas, it cannot be too carefully remembered that if the more general sciences are independent of the less general, which, on the other hand, must be dependent on them, the students of the higher must be unfit, in virtue of that very independence, to apply them to a more complex science, whose conditions they cannot sufficiently understand. If the case was clear in regard to the intrusion of the geometers into physics, it is yet more so with regard to the intrusion of the physicists intro biology; on account of the more essential difference in the nature of the two sciences. The biologists should qualify themselves for the application of the preceding sciences to their own, instead of looking to the physicists for guidance which can only lead them astray

In regard to Method, biology is indebted to physics for the most perfect models of observation and experimentation. Observations in physics are of a sufficient complexity to serve as a type for the same method in biology, if divested of their numerical considerations, which is easily done. Chemistry however can furnish an almost equally good model in simple observation. It is in experimentation that biologists may find in physics a special training for their world. As the most perfect models are found in the study of physics, and the method is singularly difficult in physiology, we see how important the contemplation of the best type must be to biologists. Such is the nature of the dependence, as to doctrine and method, of biology on physics. We turn next to its relations with Astronomy; and first, with regard to doctrine.

The relation of physiology to astronomy is more important than is usually supposed. I mean something more than the impossibility of understanding the theory of weight, and its effects upon the organism, apart from the consideration of general gravitation. I mean, besides, and more specially, that it is impossible to form a scientific conception of the conditions of vital existence without talking into the account the

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aggregate astronomical elements that characterize the planet which is the home of that vital existence. We shall see more fully in the next volume, how humanity is affected by these astronomical conditions; but we must cursorily review close relations in the present connection.

The astronomical data proper to our planet are, of course statical and dynamical. The biological importance of the statical conditions is immediately obvious. No one questions the importance to vital existence of the mass of our planet in comparison with that of the sun, which determines the intensity of gravity; or of its form, which regulates the direction of the force; or of the fundamental equilibrium and the regular oscillations of the fluids which cover the greater part of its surface, and with which the existence of living beings is closely implicated; or of its dimensions, which limit the indefinite multiplication of races, and especially the human; or of its distance from the centre of our system, which chiefly determines its temperature. Any sudden change in one or more of these conditions would largely modify the phenomena of life. But the influence of the dynamical conditions of astronomy on biological study is yet more important. Without the two conditions of the fixity of the poles as a centre of rotation, and the uniformity of the angular velocity of the earth there would be a continual perturbation of the organic media which would be incompatible with life. Bichat pointed out that the intermittence of the proper animal life is subordinate in its periods to the diurnal rotation of our planet; and we may extend the observation to all the periodical phenomena of any organism, in both the normal and pathological states, allowance being made for secondary and transient influences. Moreover, there is every reason to believe that, in every organism, the total duration of life and of its chief natural phases depends on the angular velocity proper to our planet, for we are authorized to admit that, other things being equal, the duration of life must be shorter, especially in the animal organism, in proportion as the vital phenomena succeed each other more rapidly. If the earth were to rotate much faster, the course of physiological phenomena would be accelerated in proportion, and thence life would be shorter; so that the duration of life may be regarded as dependent on the duration of the day. If the duration of the year were changed, the life of the organism would again be affected: but a yet more striking consideration is that vital existence is absolutely implicated with the form of the earth’s orbit, as has been observed before. If that ellipse were to become, instead of nearly circular, as eccentric as the orbit of a comet, both the medium and the organism would

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undergo a change fatal to vital existence. Thus the small eccentricity of the earth’s orbit is one of the main conditions of biological phenomena, almost as necessary as the stability of the earth’s rotation; and every other element of the annual motion exercises an influence, more or less marked, on biological conditions, though not so great as the one we have adduced. The inclination of the plane of the orbit for instance, determines the division of the earth into climates and, consequently, the geographical distribution of living species, animal and vegetable. And again, through the alternation of seasons, it influences the phases of individual existence in all organisms, and there is no doubt that life would be affected if the revolution of the line of the nodes were accelerated; so that its being nearly immoveable has some biological value. These considerations indicate how necessary it is for biologists to inform themselves accurately, and without any intervention, of the real elements proper to the astronomical constitution of our planet. An inexact knowledge will not suffice. The laws of the limits of variation of the different elements, or, at least, a scientific analysis of the chief grounds of their permanence, are essential to biological investigation; and these can be obtained only through an acquaintance with astronomical conceptions, both geometrical and mechanical.

It may at first appear anomalous, and a breach of the encyclopedical arrangement of the sciences, that astronomy and biology should be thus immediately and eminently connected, while two other sciences lie between. But indispensable as are physics send chemistry, astronomy and biology are, by their nature, the two principal branches of natural philosophy. They, the complements of each other, include in their rational harmony the general system of our fundamental conceptions. The solar system and Man are the extreme terms within which our ideas will for ever be included. The system first, and then Man, according to the positive course of our speculative reason: and the reverse in the active process: the laws of the system determining those of Man, and remaining unaffected by them. Between these two poles of natural philosophy the laws of physics interpose, as a kind of compliment of the astronomical laws; and again, those of chemistry, as an immediate preliminary of the biological. Such being the rational and indissoluble constitution of these sciences, it becomes why I insisted on the subordination of the study of Man to that of the system, as the primary philosophical characteristic of positive biology.

Though in the infancy of the human mind, when it was in its theo-