464 POPULAR SCIENCE MONTHLY. 



temptation to exaggerate the mental endowments of the lowest crea- 

 tures, to make their minds miniature copies of the human. Eomanes' 

 books, for instance, show over and over again how a psychologist, 

 working in the interests of mental evolution, may overestimate the 

 range and complexity of the animal consciousness. Still, this is the one 

 path that psychology can follow. The biologist, on the other hand, 

 thinks his world, when he thinks consistently, in terms of physics and 

 chemistry. He is also accustomed to think from below upwards. His 

 natural tendency, then, is to carry physical and chemical principles 

 as high in the scale of life as they will go. He has his inconsequences, 

 as the psychologist has his exaggerations; and his besetting inconse- 

 quence is to admit the presence of mind in animals higher than those 

 which he has himself examined. But science is not inconsistent be- 

 cause her representatives may sometimes nod. It is a postulate of 

 mechanistic biology that physical and chemical principles will carry 

 the biological student all the way, from the algsB to man. Conscious- 

 ness does not fall within his horizon. Until, then, the interactionist has 

 converted his biological colleagues to vitalism, and thence to the ad- 

 mission of mental process as an equivalent of physical energy, we must 

 conclude that the two fields of enquiry, the psychological and the 

 biological, do not overlap. There is no reason why the biologist, 

 granted a steady increase of natural knowledge, should not some day 

 reduce all the movements, say, of the monkeys, to physico-chemical 

 terms, to a system of simple or complex 'reflexes.' That is what he is 

 on the way to do. On the other hand, the reduction of all the move- 

 ments of Paramecium to a single 'reflex' type does not prove to the 

 psychologist that the creature has not (or has not had) a mind. 

 Biolog}' and psychology, if I may change the metaphor, meet and pass 

 on a double track. They do not collide, but neither do they turn out 

 to be two halves of a single train of thought. 



We may ask, secondly, for a clearer understanding of what has 

 been called the 'objective criterion of mind.' The phrase is open to the 

 objection that it contains a contradictio in adjectivo; how can there 

 be an objective criterion of the subjective ? But we may waive this, and 

 assume that an empirical correlation is possible. Let us suppose, then, 

 that biology and psychology agree to ask the question : How are we to 

 tell, by watching a lower animal's movements, whether or not it has a 

 mind? And let us suppose, further, that they are agreed upon their 

 answer. The answer must be of this kind: If you see so and so, then 

 you may infer the presence of consciousness. Beyond that, no answer 

 has gone, and no answer can possibly go. Because this animal does this 

 thing, it has a mind ; this other animal does not do this thing, therefore 

 — what? Therefore, we do not know whether it has a mind. It may 

 not, of course, but then again, it may. The biologist, 1 repeat, may 



