8 
INTRODUCTION. 
higher, and even in that of men other than the sceptic 
himself. For all objections which could apply to the use 
of this criterion of mind in the animal kingdom would 
apply with equal force to the evidence of any mind other 
than that of the individual objector. This is obvious, 
because, as I have already observed, the only evidence we 
can have of objective mind is that which is furnished by 
objective activities ; and as the subjective mind can never 
become assimilated with the objective so as to learn by 
direct feeling the mental processes which there accompany 
the objective activities, it is clearly impossible to satisfy 
any one who may choose to doubt the validity of inference, 
that in any case other than his own mental processes ever 
do accompany objective activities. Thus it is that philo- 
sophy can supply no demonstrative refutation of idealism, 
even of the most extravagant form. Common sense, how- 
ever, universally feels that analogy is here a safer guide 
to truth than the sceptical demand for impossible evi- 
dence; so that if the objective existence of other or- 
ganisms and their activities is granted — without which 
postulate comparative psychology, like all the other 
sciences, would be an unsubstantial dream — common 
sense will always and without question conclude that the 
activities of organisms other than our own, when analogous 
to those activities of our own which we know to be accom- 
panied by certain mental states, are in them accompanied 
by analogous mental states. 
The theory of animal automatism, therefore, which is 
usually attributed to Descartes (although it is not quite 
clear how far this great philosopher really entertained the 
theory), can never be accepted by common sense ; and even 
as a philosophical speculation it will be seen, from what has 
just been said, that by no feat of logic is it possible to 
make the theory apply to animals to the exclusion of 
man. The expression of fear or affection by a dog in- 
volves quite as distinctive and complex a series of neuro- 
muscular actions as does the expression of similar emotions 
by a human being; and therefore, if the evidence of 
corresponding mental states is held to be inadequate in 
the one case, it must in consistency be held similarly 
