F. M. CAMPBELL-ON INSTINCT. 
121 
Definition of Instinct. 
Romanes has defined Instinct as (< reflex action into which there 
is imported the element of consciousness. The term is therefore a 
generic one, comprising all those faculties of mind which are con¬ 
cerned in conscious and adaptive action, antecedent to individual 
experience, without necessary knowledge of the relation between 
means employed and ends attained, hut similarly performed under 
similar and frequently-recurring circumstances by all the individuals 
of the same species.” * The same author writes : “ The most im¬ 
portant point to observe in the first instance is that instinct involves 
mental operations; for this is the only point that serves to distinguish 
instinctive from reflex action. Reflex action is non-mental neuro¬ 
muscular adaptation to appropriate stimuli; but instinctive action is 
this and something more ; there is in it the element of mind. No 
doubt it is often difficult, or even impossible, to decide whether or 
not a given action implies the presence of the mind-element— i.e. 
conscious as distinguished from unconscious adaptation; hut this is 
altogether a separate matter, and has nothing to do with the 
question of defining instinct in a manner which shall he formally 
exclusive, on the one hand of reflex action, and on the other of 
reason. As Yirchow truly observes, ‘ it is difficult or impossible to 
draw the line between instinctive or reflex action; ’ but at least the 
difficulty may be narrowed down into deciding in particular cases 
whether or not an action falls into this or that category of definition; 
there is no reason why the difficulty should arise on account of any 
ambiguity of the definitions themselves. Therefore I endeavour to 
draw as sharply as possible the line which in theory should be taken 
to separate instinctive from reflex action; and this line, as I have 
already said, is constituted by the boundary of non-mental or un¬ 
conscious adjustment, with adjustment in which there is concerned 
consciousness or mind.” f 
Most naturalists would be satisfied with the rough sketch of the 
meaning of “ Instinct ” as given in the chapter containing the 
sentence already quoted from Darwin, and it is in this sense they 
have hitherto applied it. Rut it is this very use of the w r ord that 
renders a definition necessary to the psychologist when discussing 
mental evolution, should he decide to retain it. All definitions are 
inherently faulty, and particularly those of psychical characteristics; 
inasmuch as any attempt to separate such characteristics impairs the 
individual existence, in which alone they are recognisable. Evi¬ 
dently the definition must be theoretical, as Romanes admits. The 
limitation of the meaning of any word increases the difficulty of its 
application. But in the case of “ Instinct” there is more than this. 
The very definition given by Romanes precludes observers from 
being sure that they are correct in employing it. This cannot be 
said of “ Intelligence,” the evidence of the possession of which is 
the profiting by experience or the adaptation to new conditions. 
There is however no such test of “ Instinct ” as defined by Romanes. 
Eor if an instinctive act be not modified perceptibly to an observer 
* ‘ Mental Evolution in Animals,’ p. 159. \ lb., p. 160. 
