June 5, 1879] 



NATURE 



123 



is upon this topic that I should now like to offer a few 

 remarks. 



Although Mr. Henslow has not been very fortunate in 

 the expression of his views, I think he has before his 

 mind the most essential, as well as perhaps the most con- 

 spicuous, quality wherein animal intelligence differs from 

 human. He says : " It has always seemed to me that 

 brute reasoning is always practical and never abstract. 

 They do wonderful things suggested by the objective facts 

 before them, but, I think, never go beyond it. Thus, a 

 dog left in a room alone rang the bell to fetch the ser- 

 vant. Had not the dog been taught to ring the bell 

 (which, on inquiry, proved to have been the case), it 

 would have been abstract reasoning, but it was only prac- 

 tical. The Arctic fox — too wary to be shot like the first 

 who took a bait tied to a string, which was attached to 

 the trigger of a gun -would dive under the snow, and so 

 pull the bait down below the line of fire. This is purely 

 practical reasoning ; but had the fox pulled the string first 

 out of the line of fire in order to discharge the gun, and 

 then to get the bait, that would have been abstract reason- 

 ing which he could not attain to." 



To this Dr. Rae replies : " To pull the bait downwards 

 oiit of the line of fire was the only safe way for the fox to 



have acted Had he used what Mr. Henslow calls 



' abstract reasoning ' — which, I presume, means pulling 

 the bait, not the line, to one side out of the line of fire— the 

 fox would certainly have been shot, as the bait could not 

 have been moved more than four or five inches from the 

 wooden stake through which the bait-line passes. 



" If Mr. Henslow really means that the fox should have 

 shown his powers of ' abstract reasoning' by going up to 

 the line of fire between the gun and the bait, and then 

 pulled the string until the gun went off, I think the 

 chances of reynard's ever eating the bait would be very 

 small indeed. I have known him do what showed equal 

 or greater intelligence, namely, cut the bait-string, as 

 already mentioned." 



It having been thus clearly shown that the "practical 

 reasoning " of the fox was more to the point than the 

 "abstract reasoning" of his critic, and several others of 

 your correspondents having supplied more or less well- 

 authenticated instances of the display of deliberative rea- 

 soning by brutes, Mr. Henslow concluded his part in the 

 correspondence by modifying his original statement 

 thus : — " I will abandon my notion of abstract reasoning, 

 at least as hitherto described, for I now think that what 

 1 meant by the want of the faculty would be better de- 

 scribed as an impotence, or, at least, a feebleness of 

 mind in concatenating correlative ideas ; or, perhaps, a 

 want of receptivity of the suggestiveness of things will 

 express my meaning." Owing, perhaps, to a feebleness 

 of mind in concatenating correlative ideas, or perhaps to 

 a want of receptivity of the suggestiveness of things, for 

 my own part I cannot perceive these words to express 

 any meaning at all — or, at least, any meaning that is not 

 flagrantly absurd. I have never known an animal unable 

 to concatenate the idea of eating with the correlative idea 

 of the thing suited to be eaten, and very few among the 

 higher animals show any want of receptivity of the sug- 

 gestiveness of such a thing as a whip. The truth is Mr. 

 Henslow has only darkened his meaning by this latest 

 multiplication of words. What he originally intended to 

 say is, not that animals do not possess any power of ab- 

 stract thinking, but that this power is in them feeble as 

 compared with what it is in man. Abstract thinking 

 means thinking in or of abstractions, i.e., of qualities as 

 apart from particular objects. Now it would be absurd 

 to maintain that no animal has any idea of quality except 

 as in association with particular objects of past experience. 

 Give a cat or a dog some kind of meat or cake which the 

 animal has never before met with, and the careful examina- 

 tion which the morsel undergoes before it is consigned to 

 the mouth proves that the animal has properly abstract 



ideas of sweet, bitter, hot, nauseous, or, in g«ji\cral, good 

 for eating and bad for eating, i.e., abstract ideas of quality 

 as apart from the object examined — the motive of the 

 examination clearly being to ascertain which general idea 

 of quality is appropriate to the particular object examined. 

 Thus Mr. Henslow cannot mean that animals possess no 

 power at all of abstract thought. What he must mean is 

 that this power is manifested in an extremely undeveloped 

 form, the mind of an animal being only furnished with 

 abstract ideas of the simplest or least elaborated type, 

 and being therefore unable to carry on for any consider- 

 able distance the process of forming and joining ideas 

 irrespective of suggestions supplied by immediate sense- 

 perceptions. In other words, as Mr. Henslow himself 

 very clearly states the case in one of his earlier letters, 

 "it is this mental reflection which seems to me to be 

 wanting in animals." 



Taking, then, this as the only meaning which Mr. Hens- 

 low has to convey, it is, I think, the only meaning which 

 with philosophical justice he can have to convey. For the 

 more that we push analysis into the region of brute 

 psychology, the more do we become convinced that the 

 only very considerable difference between it and human 

 psychology consists in the comparatively small develop- 

 ment of the power of "mental reflection." 



And here I may remark that this is just the difference 

 which the theory of descent would lead us to anticipate as 

 the chief, if not the ooly, difference ; for it is evident that 

 this difference has reference to the highest qualities of 

 mind — i.e., those most removed from simple mechanical 

 responses to stimuli supplied by the senses — and therefore 

 to the qualities which must have been of the most recent 

 development. The tree psychological has been a long 

 time in growing ; its roots are constituted by mere excita- 

 bility, reflex action is its stem, its branches are the asso- 

 ciation of ideas, the emotions are its leaves, and the 

 faculty of abstract thought is a single blossom borne upon 

 its topmost spray. And if we compare this tree with that 

 of zoologry, we find that the single blossom of the one 

 corresponds with the highest product of the other. Homo 

 sapiens is the lord of creation, because, having sprung 

 from the primates he started with some little power of 

 abstract thought, which, through the instrumentality of 

 continuously improving language, was forced_on by natural 

 selection at a probably astounding pace. 



So far, then, as the theory of descent is concerned, there 

 is no serious difficulty presented by this chief point of 

 difference between animal and human intelligence.^ I 

 think, however, that both in this connection, and also for 

 the sake of comparative psychology, it is desirable to say 

 that although Mr. Henslow has, in my opinion, stated 

 the only great difference that obtains between human and 

 animal psychology, there is no reason to think that this 

 difference is so great or absolute as he appears to suppose.^ 



* I may here remark that a great deal too much stress seems to me to be 

 laid by many writers on the presence of self -consciousness in man as a 

 feature distinguishing his mind from that of animals. For this faculty, it 

 seems to me, is obviou-sly one that mmt .arise so soon as the power of forming 

 abstract ideas has advanced sufficiently far to admit of an animal thinking 

 of itself as distinct from its surroundings. And this is surely not any so 

 enormous an advance as to be impossible without supernatural assistance. A 

 semi-human animal might well have had an abstract idea of thou, you, and 

 they, and also an abstract idea of its own body as being more or less similar 

 to that of its fellows. From this to an abstract conception of I, as distin- 

 guished from thou and not I, the transition seems sufficiently easy ; and 

 when once the idea of self began to dawn, it would be assisted by reflection, 

 rentiering past slates of consciousness objective to present ones. But the 

 idea of scup/us the power of introspection is all that can be meant by self- 

 consciousness. 



« In saying that Mr. Henslow has stated this difference to be the only one 

 that obtains between human and animal psychology,^ 1 do not forget the 

 remarks with v/hich he concludes his corre.^pondence. These remarks may be 

 summed up in his own words— animals ''cannot be self-conscious, cannot 

 conceive of God, and can neither be moral nor immoral." A-: all these 

 distinctiins between human intelligence and animal intelligence clearly rest 

 upon, or are included in, the distinction above considered in the t'^'^*, it is 

 nectiless to occupy space with considering them in detail. Although I h.aye 

 myself maintained that on the theory of evolution we might antecedently 

 expect the more intelligent and sympathetic of the higher animals to present 

 the germs of a moral sense, and further, that in the case of dogs this expec- 

 tation seems sometimes to be realised, this, of course, is a widely different 



