INTRODUCTION. 
3 
ties, on pinching or tickling his feet they are drawn sud- 
denly away from the irritation, although the man is quite 
unconscious of the adaptive movement of his muscles ; 
the lower nerve-centres of the spinal cord are competent 
to bring about this movement of adaptive response with- 
out requiring to be directed by the brain. This non- 
mental operation of the lower nerve-centres in the pro- 
duction of apparently intentional movements is called 
Reflex Action, and the cases of its occurrence, even within 
the limits of our own organism, are literally numberless. 
Therefore, in view of such non-mental nervous adjust- 
ment, leading to movements which are only in appearance 
intentional, it clearly becomes a matter of great difficulty 
to say in the case of the lower animals whether any action 
which appears to indicate intelligent choice is not really 
action of the reflex kind. 
On this whole subject of mind-like and yet not truly 
mental action I shall have much to say in my subsequent 
treatise, where I shall be concerned among other things 
with tracing the probable genesis of mind from non- 
mental antecedents. But here it is sufficient merely to 
make this general statement of the fact, that even within 
the experience supplied by our own organisms adaptive 
movements of a highly complex and therefore apparently 
purposive character may be performed without any real 
purpose, or even consciousness of their performance. It 
thus becomes evident that before we can predicate the 
bare existence of mind in the lower animals, we need 
some yet more definite criterion of mind than that which 
is supplied by the adaptive actions of a living organism, 
howsoever apparently intentional such actions may be. 
Such a criterion I have now to lay down, and I think it is 
one that is as practically adequate as it is theoretically 
legitimate. 
Objectively considered, the only distinction between 
adaptive movements due to reflex action and adaptive 
movements due to mental perception, consists in the 
former depending on inherited mechanisms within the 
nervous system being so constructed as to effect particular 
adaptive movements in response to particular stimuli 
