Let us now see how he carries this passionate enthusiasm for knowledge into the humblest researches of zoology:—
Among natural objects, some exist unchanged through all eternity, while others are generated and decay. The former are divinely glorious, but being comparatively inaccessible to our means of observation, far less is known of them than we could wish; while perishable plants and animals offer abundant opportunities of study to us who live under the same conditions with them. Each science has a charm of its own. For knowledge of the heavenly bodies is so sublime a thing that even a little of it is more delightful than all earthly science put together; just as the smallest glimpse of a beloved beauty is more delightful than the fullest and nearest revelation of ordinary objects; while, on the other hand, where there are greater facilities for observation, science can be carried much further; and our closer kinship with the creatures of earth is some compensation for the interest felt in that philosophy which deals with the divine. Wherefore, in our discussions on living beings we shall, so far as possible, pass over nothing, whether it rank high or low in the scale of estimation. For even such of them as displease the senses, when viewed with the eye of reason as wonderful works of Nature afford an inexpressible pleasure to those who can enter philosophically into the causes of things. For, surely, it would be absurd and irrational to look with delight at the images of such objects on account of our interest in the pictorial or plastic skill which they exhibit, and not to take still greater pleasure in a scientific explanation of the realities themselves. We ought not then to shrink with childish disgust from an examination of the lower animals, for there is something wonderful in all the works of Nature; and we may repeat what Heracleitus is reported to have said to certain strangers who had come to visit him, but hung back at the door when they saw him warming himself before a fire, bidding them come in boldly, for that there also there were gods; not allowing ourselves to call any creature common or unclean, because there is a kind of natural beauty about them all. For, if anywhere, there is a pervading purpose in the works of Nature, and the realisation of this purpose is the beauty of the thing. But if anyone should look with contempt on the scientific examination of the lower animals, he must have the same opinion about himself; for the greatest repugnance is felt in looking at the parts of which the human body is composed, such as blood, muscles, bones, veins, and the like.[193] Similarly, in discussing any part or organ we should consider that it is not for the matter of which it consists that we care, but for the whole form; just as in talking about a house it is not bricks and mortar and wood that we mean; and so the theory of Nature deals with the essential structure of objects, not with the elements which, apart from that structure, would have no existence at all.[194]
It is well for the reputation of Aristotle that he could apply himself with such devotion to the arduous and, in his time, inglorious researches of natural history and comparative anatomy, since it was only in those departments that he made any real contributions to physical science. In the studies which were to him the noblest and most entrancing of any, his speculations are one long record of wearisome, hopeless, unqualified delusion. If, in the philosophy of practice and the philosophy of art, he afforded no real guidance at all, in the philosophy of Nature his guidance has always led men fatally astray. So far as his means of observation extended, there was nothing that he did not attempt to explain, and in every single instance he was wrong. He has written about the general laws of matter and motion, astronomy, chemistry, meteorology, and physiology, with the result that he has probably made more blunders on those subjects than any human being ever made before or after him. And, if there is one thing more astounding than his unbroken infelicity of speculation, it is the imperturbable self-confidence with which he puts forward his fallacies as demonstrated scientific certainties. Had he been right, it was no ‘slight or partial glimpses of the beloved’ that would have been vouchsafed him, but the ‘fullest and nearest revelation’ of her beauties. But the more he looked the less he saw. Instead of drawing aside he only thickened and darkened the veils of sense which obscured her, by mistaking them for the glorious forms that lay concealed beneath.
Modern admirers of Aristotle labour to prove that his errors were inevitable, and belonged more to his age than to himself; that without the mechanical appliances of modern times science could not be cultivated with any hope of success. But what are we to say when we find that on one point after another the true explanation had already been surmised by Aristotle’s predecessors or contemporaries, only to be scornfully rejected by Aristotle himself? Their hypotheses may often have been very imperfect, and supported by insufficient evidence; but it must have been something more than chance which always led him wrong when they were so often right. To begin with, the infinity of space is not even now, nor will it ever be, established by improved instruments of observation and measurement; it is deduced by a very simple process of reasoning, of which Democritus and others were capable, while Aristotle apparently was not. He rejects the idea because it is inconsistent with certain very arbitrary assumptions and definitions of his own, whereas he should have rejected them because they were inconsistent with it. He further rejects the idea of a vacuum, and with it the atomic theory, entirely on à priori grounds, although, even in the then existing state of knowledge, atomism explained various phenomena in a perfectly rational manner which he could only explain by unmeaning or nonsensical phrases.[195] It had been already maintained, in his time, that the apparent movements of the heavenly bodies were due to the rotation of the earth on its own axis.[196] Had Aristotle accepted this theory one can imagine how highly his sagacity would have been extolled. We may, therefore, fairly take his rejection of it as a proof of blind adherence to old-fashioned opinions. When he argues that none of the heavenly bodies rotate, because we can see that the moon does not, as is evident from her always turning the same side to us,[197] nothing is needed but the simplest mathematics to demonstrate the fallacy of his reasoning. Others had surmised that the Milky Way was a collection of stars, and that comets were bodies of the same nature as planets. Aristotle is satisfied that both are appearances like meteors, and the aurora borealis—caused by the friction of our atmosphere against the solid aether above it. A similar origin is ascribed to the heat and light derived from the sun and stars; for it would be derogatory to the dignity of those luminaries to suppose, with Anaxagoras, that they are formed of anything so familiar and perishable as fire. On the contrary, they consist of pure aether like the spheres on which they are fixed as protuberances; though how such an arrangement can co-exist with absolute contact between each sphere and that next below it, or how the effects of friction could be transmitted through such enormous thicknesses of solid crystal, is left unexplained.[198] By a happy anticipation of Roemer, Empedocles conjectured that the transmission of light occupied a certain time: Aristotle declares it to be instantaneous.[199]
On passing to terrestrial physics, we find that Aristotle is, as usual, the dupe of superficial appearances, against which other thinkers were on their guard. Seeing that fire always moved up, he assumed that it did so by virtue of a natural tendency towards the circumference of the universe, as opposed to earth, which always moved towards the centre. The atomists erroneously held that all matter gravitated downwards through infinite space, but correctly explained the ascent of heated particles by the pressure of surrounding matter, in accordance, most probably, with the analogy of floating bodies.[200] Chemistry as a science is, of course, an entirely modern creation, but the first approach to it was made by Democritus, while no ancient philosopher stood farther from its essential principles than Aristotle. He analyses bodies, not into their material elements, but into the sensuous qualities, hot and cold, wet and dry, between which he supposes the underlying substance to be perpetually oscillating; a theory which, if it were true, would make any fixed laws of nature impossible.
It might have been expected that, on reaching physiology, the Stagirite would stand on firmer ground than any of his contemporaries. Such, however, is not the case. As already observed, his achievements belong entirely to the dominion of anatomy and descriptive zoology. The whole internal economy of the animal body is, according to him, designed for the purpose of creating and moderating the vital heat; and in apportioning their functions to the different organs he is entirely dominated by this fundamental error. It was a common notion among the Greeks, suggested by sufficiently obvious considerations, that the brain is the seat of the psychic activities. These, however, Aristotle transports to the heart, which, in his system, not only propels the blood through the body, but is also the source of heat, the common centre where the different special sensations meet to be compared, and the organ of imagination and of passion. The sole function of the brain is to cool down the blood—a purpose which the lungs also subserve. Some persons believe that air is a kind of food, and is inhaled in order to feed the internal fire; but their theory would involve the absurd consequence that all animals breathe, for all have some heat. Anaxagoras and Diogenes did, indeed, make that assertion, and the latter even went so far as to say that fish breathe with their gills, absorbing the air held in solution by the water passed through them—a misapprehension, says Aristotle, which arose from not having studied the final cause of respiration.[201] His physiological theory of generation is equally unfortunate. In accordance with his metaphysical system, hereafter to be explained, he distinguishes two elements in the reproductive process, of which one, that contributed by the male, is exclusively formative; and the other, that contributed by the female, exclusively material. The prevalent opinion was evidently, what we know now to be true, that each parent has both a formative and a material share in the composition of the embryo. Again, Aristotle, strangely enough, regards the generative element in both sexes as an unappropriated portion of the animal’s nutriment, the last and most refined product of digestion, and therefore not a portion of the parental system at all; while other biologists, anticipating Mr. Darwin’s theory of pangenesis in a very wonderful manner, taught that the semen is a conflux of molecules derived from every part of the body, and thus strove to account for the hereditary transmission of individual peculiarities to offspring.[202]
All these, however, are mere questions of detail. It is on a subject of the profoundest philosophical importance that Aristotle differs most consciously, most radically, and most fatally from his predecessors. They were evolutionists, and he was a stationarist. They were mechanicists, and he was a teleologist. They were uniformitarians, and he was a dualist. It is true that, as we mentioned at the beginning of this chapter, Mr. Edwin Wallace makes him ‘recognise the genesis of things by evolution and development,’ but the meaning of this phrase requires to be cleared up. In one sense it is, of course, almost an identical proposition. The genesis of things must be by genesis of some kind or other. The great question is, what things have been evolved, and how have they been evolved? Modern science tells us, that not only have all particular aggregates of matter and motion now existing come into being within a finite period of time, but also that the specific types under which we arrange those aggregates have equally been generated; and that their characteristics, whether structural or functional, can only be understood by tracing out their origin and history. And it further teaches us that the properties of every aggregate result from the properties of its ultimate elements, which, within the limits of our experience, remain absolutely unchanged. Now, Aristotle taught very nearly the contrary of all this. He believed that the cosmos, as we now know it, had existed, and would continue to exist, unchanged through all eternity. The sun, moon, planets, and stars, together with the orbs containing them, are composed of an absolutely ungenerable, incorruptible substance. The earth, a cold, heavy, solid sphere, though liable to superficial changes, has always occupied its present position in the centre of the universe. The specific forms of animal life—except a few which are produced spontaneously—have, in like manner, been preserved unaltered through an infinite series of generations. Man shares the common lot. There is no continuous progress of civilisation. Every invention and discovery has been made and lost an infinite number of times. Our philosopher could not, of course, deny that individual living things come into existence and gradually grow to maturity; but he insists that their formation is teleologically determined by the parental type which they are striving to realise. He asks whether we should study a thing by examining how it grows, or by examining its completed form: and Mr. Wallace quotes the question without quoting the answer.[203] Aristotle tells us that the genetic method was followed by his predecessors, but that the other method is his. And he goes on to censure Empedocles for saying that many things in the animal body are due simply to mechanical causation; for example, the segmented structure of the backbone, which that philosopher attributes to continued doubling and twisting—the very same explanation, we believe, that would be given of it by a modern evolutionist.[204] Finally, Aristotle assumes the only sort of transformation which we deny, and which Democritus equally denied—that is to say, the transformation of the ultimate elements into one another by the oscillation of an indeterminate matter between opposite qualities.
VI.
The truth is that while our philosopher had one of the most powerful intellects ever possessed by any man, it was an intellect strictly limited to the surface of things. He was utterly incapable of divining the hidden forces by which inorganic nature and life and human society are moved. He had neither the genius which can reconstruct the past, nor the genius which partly moulds, partly foretells the future. But wherever he has to observe or to report, to enumerate or to analyse, to describe or to define, to classify or to compare; and whatever be the subject, a mollusc or a mammal, a mouse or an elephant; the structure and habits of wild animals; the different stages in the development of an embryo bird; the variations of a single organ or function through the entire zoological series; the hierarchy of intellectual faculties; the laws of mental association; the specific types of virtuous character; the relation of equity to law; the relation of reason to impulse; the ideals of friendship; the different members of a household; the different orders in a State; the possible variations of political constitutions, or within the same constitution; the elements of dramatic or epic poetry; the modes of predication; the principles of definition, classification, judgment, and reasoning; the different systems of philosophy; all varieties of passion, all motives to action, all sources of conviction;—there we find an enormous accumulation of knowledge, an unwearied patience of research, a sweep of comprehension, a subtlety of discrimination, an accuracy of statement, an impartiality of decision, and an all-absorbing enthusiasm for science, which, if they do not raise him to the supreme level of creative genius, entitle him to rank a very little way below it.
It was natural that one who ranged with such consummate mastery over the whole world of apparent reality, should believe in no other reality; that for him truth should only mean the systematisation of sense and language, of opinion, and of thought. The visible order of nature was present to his imagination in such precise determination and fulness of detail that it resisted any attempt he might have made to conceive it under a different form. Each of his conclusions was supported by analogies from every other department of enquiry, because he carried the peculiar limitations of his thinking faculty with him wherever he turned, and unconsciously accommodated every subject to the framework which they imposed. The clearness of his ideas necessitated the use of sharply-drawn distinctions, which prevented the free play of generalisation and fruitful interchange of principles between the different sciences. And we shall have occasion to show hereafter, that, when he attempted to combine rival theories, it was done by placing them in juxtaposition rather than by mutual interpenetration. Again, with his vivid perceptions, it was impossible for him to believe in the justification of any method claiming to supersede, or even to supplement, their authority. Hence he was hardly less opposed to the atomism of Democritus than to the scepticism of Protagoras or the idealism of Plato. Hence, also, his dislike for all explanations which assumed that there were hidden processes at work below the surface of things, even taking surface in its most literal sense. Thus, in discussing the question why the sea is salt, he will not accept the theory that rivers dissolve out the salt from the strata through which they pass, and carry it down to the sea, because river-water tastes fresh; and propounds in its stead the utterly false hypothesis of a dry saline evaporation from the earth’s surface, which he supposes to be swept seawards by the wind.[205] Even in his own especial province of natural history the same tendency leads him astray. He asserts that the spider throws off its web from the surface of its body like a skin, instead of evolving it from within, as Democritus had taught.[206] The same thinker had endeavoured to prove by analogical reasoning that the invertebrate animals must have viscera, and that only their extreme minuteness prevents us from perceiving them; a view which his successor will not admit.[207] In fact, wherever the line between the visible and the invisible is crossed, Aristotle’s powers are suddenly paralysed, as if by enchantment.