230 



SCIENCE. 



the contrary, the unions which these affinities by themselves 

 produce can only be reached through the dissolution and 

 destruction of living bodies. The subjugation of chemical 

 forces under some higher form of energy, which works 

 them for the continued maintenance of a separate individu- 

 ality — this is of the very essence of Life. The destruction 

 of that separateness is of the very essence of death. It is 

 not Life, but the cessation of Life, which, in this sense and 

 after this manner, effects a chemical union of the elements 

 of the body with the elements around it. There is indeed 

 an adjustment — a close, an intricate adjustment — between 

 these and the living body ; but it is an adjustment of them 

 under the controlling energy of a power which cannot be 

 identified with any other, and which always presents pheno- 

 mena peculiar to itself. Under that power we see that the 

 laws and forces of chemical affinity, as exhibited apart from 

 Life, are held, as it were, to service — compelled, indeed, to 

 minister but not allowed to rule. Through an infinite 

 variety of organisms, this mysterious subordination is main- 

 tained, ministering through an ascending series to higher 

 and higher grades of sensation, perception, consciousness, 

 and thought. 



And here we come in sight of the highest adjustment of all. 

 Sensation, perception, consciousness, and thought — these, if 

 they be not the very essence of Life, are at least — in their 

 order — its highest accompaniments and result. They are the 

 ultimate facts, they are the final realities, to which all lesser 

 adjustments are themselves adjusted. For, as the elemen- 

 tary substances and the elementary forces of Nature which 

 are used in the building of the body are there held by the 

 energies of Life under a special and peculiar relation to those 

 same elements and to those same forces outside the body, 

 so also are they held in peculiar relations to those character- 

 istic powers in which we are compelled to recognize the rudi- 

 mentary faculties of mind, Sensation is the first of these, 

 and if it be the lowest, it is at least the indispensable basis 

 of all the rest. As such, it cannot be studied too attentively 

 in the first stages of its appearance, if we desire to under- 

 stand the unity of which it is the index and result. We 

 have seen that the mechanism of living bodies is one 

 throughout the whole range of animal Life — one in its gen- 

 eral plan, and one even in the arrangement of many of its 

 details. We have seen, too, that this unity rests upon that 

 other — in virtue of which all organisms depend for the 

 maintenance of their life, upon adjustments to certain 

 physical laws which are held, as it were, in vassalage, and 

 compelled to service ; doing in that service what they never 

 do alone, and not doing in that service what they always do 

 when freed from it. 



And now we have to ask what that service is ? We can 

 only say that it is the service of Life in all its manifestations, 

 from those which we see in the lowest creatures up to the 

 highest of which, in addition, we are conscious in ourselves. 

 I say " in addition " — because this is the fundamental les- 

 son of physiology and of comparative anatomy — that the 

 principle and the mechanism of sensation are the same in 

 all creatures, at least in all which have the rudiments of a 

 nervous system. This identity of principle and of struc- 

 ture in the machinery of sensation, taken together with the 

 identity of the outward manifestations which accompany 

 and indicate its presence in animals, makes it certain that 

 in itself it is everywhere the same. This does not mean, of 

 course — very far from it — that the range of pleasure or of 

 pain consequent on sensation — still less the range of intel- 

 ligent perception — is the same throughout the animal king- 

 dom. The range of pleasure or of pain, and still more the 

 range of intelligent perception, depends on the association 

 of higher faculties with mere sensation, and upon other 

 peculiarities or conditions of organization. We all know 

 by our own experience, when comparing ourselves with 

 ourselves in different states of health or of disease, and by 

 observing the like facts in others, that the degree of pleas- 

 ure or of Buffering, of emotion or of intellectual activity, 



which is connei ted with sensation, may lie almost infinitely 



various according to various conditions of the hod)'. Hut 

 this does not affect the general proposition that sensation is 

 in itself one thing throughout the animal kingdom. It 

 cannot be defined in language, because all language is 

 founded on it, assume: it I" be known, and uses the meta- 

 phors it supplies for the expression of our highest intellec- 



tual conceptions. But though it cannot be defined, this at 

 least we can say concerning it, that sensation is the charac- 

 teristic property of animal life ; that it is an affection of the 

 " anima," of that which distinguishes animate from inani- 

 mate things, and that as such it constitutes one of the most 

 essential of the fundamental properties of mind. So true 

 is this, that the very word " idea," which has played a me- 

 morable part in the history of speculation, and which in 

 common speech has now come to be generally associated 

 with the highest intellectual abstractions, has had in modern 

 philosophy no other definite meaning than the impressions 

 or mental images received through the senses. This is the 

 meaning attached to it (although, perhaps, no writer has 

 ever adhered to it with perfect consistency) in the writings 

 of Descartes, of Locke, and of Bishop Berkeley ; and it is 

 well worthy of remark that the most extreme doctrine of 

 Idealism, which denies the reality of matter, and, indeed, 

 the reality of everything except mind, is a doctrine which 

 may be as logically founded upon sensation in a Zoophyte 

 as upon sensation in a Man. The famous proposition of 

 Bishop Berkeley, which he considers as almost self-evi- 

 dently true, "that the various sensations, or ideas imprinted 

 on the sense, cannot exist otherwise than in the mind per- 

 ceiving them," is a proposition clearly applicable to all 

 forms of sensation whatever. For every sensation of an 

 organism is equally in the nature of an " idea" in being an 

 affection of the living principle, which alone is susceptible 

 of such affections ; and it is plainly impossible to conceive 

 any sense-impression whatever as existing outside a living 

 and perceiving creature. 



We are now, indeed, so accustomed to attach the word 

 " idea " to the highest exercises of mind, and to confine the 

 word " mind " itself to some of its higher manifestations, 

 that it may startle some men to be told that sensation is in 

 itself a mental affection. We have, however, only to con- 

 sider for a moment how inseparably connected sensation is 

 with appetite and with perception, to be convinced that in 

 the phenomena of sensation we have the first raw materials 

 and the first small beginnings of Intelligence and of Will. It 

 is this fundamental character of sensation which explains and 

 justifies the assertion of philosophers — an assertion which at 

 first sight appears to be a mere paradox — that the " ideas " 

 we receive through th ; senses have no " likeness " to the ob- 

 jects they represent. For that assertion, after all, means noth- 

 ing more than this — that the impressions made by external 

 things upon living beings through the senses, are in them- 

 selves mental impressions, and as such cannot be conceived 

 as like in their own nature to inanimate and external ob- 

 jects. It is the mental quality of all sensation, considered 

 in itself, which is really affirmed in this denial of likeness 

 between the affections of sense and the things which pro- 

 duce those affections in us. It is one of the many forms in 

 which we are compelled to recognize the inconceivableness 

 of any sort of resemblance between Mind and Matter, be- 

 tween external things and our own perceptive powers. 



And yet it is across this great gulf of difference — appa- 

 rently so broad and so profound — that the highest unity of 

 Nature is nevertheless established. Matter built up and 

 woven into "organs" under the powers of Life is the strong 

 foundation on which this unity is established. It is the 

 unity which exists between the living organism and the ele- 

 ments around it which renders that organism the appro- 

 priate channel of mental communication with the external 

 world, and a faithful interpreter of its signs. And this the 

 organism is — not only by virtue of its substance and com- 

 position, but also ana especially by virtue of its adjusted 

 structures. All the organs of sense discharge their func- 

 tions in virtue of a purely mechanical adjustment between 

 the structure of the organ and the particular form of exter- 

 nal force which it is intended to receive and to transmit, 

 How fine those adjustments are can best be understood 

 when we remember that the retina of the eye is a machine 

 which measures and distinguishes between vibrations which 

 arc now known to differ from each other by only a few mil- 

 lionthsof an inch. Yet this amount af difference is re- 

 corded and made instantly appreciable in the sensations of 

 color by the adjusted mechanism of the eye. Another ad- 

 justment, precisely the same in principle, between the vi- 

 brations of Sound and the structure of the ear, enables 

 those vibrations to be similarly distinguished in another 



