DEFINITION OF INSTINCTIVE BEHAVIOUR 67 
the young, with nest-building, with migration, etc., these 
actions are surely to be classed as instinctive ; and yet they are 
exceedingly variable and unpredictable in detail ; all that we 
can predict is the general trend of the varying actions which 
result from varying stimuli under varying conditions, and 
which function to some determinate biological end.” 
Mr. Marshall then proceeds to argue that we are “ warranted 
in speaking of the ethical instincts, of the patriotic instincts, 
of the benevolent instincts, and of the artistic instincts ;” and 
thus leads up to the position, to be further elaborated in his 
work, that there exists in man a religious instinct which has 
fulfilled a function of biological value in the development of 
our race. Now, here again there is much in popular usage of 
the words instinct and instinctive which lends support, for 
what it is worth, to Mr. Marshall's very broad conception of 
the range of instinct. Again and again we hear, in the pulpit 
and elsewhere, of the religious instinct ; we hear, too, of the 
benevolent, patriotic, and artistic instincts, and more besides. 
But what we are endeavouring to define is a type of behaviour 
which, as such, is prior to instruction and experience. Can we 
affirm that patriotic and religious behaviour conforms to such 
a type? Is it unquestionably congenital and not acquired ? 
If we are forced to give negative answers to these questions we 
must regard Mr. Marshall’s conception of instinct (one inclusive 
of multifarious tendencies which have a biological value) as 
too broad and too vague to be of any service to us at this stage 
of our study of animal behaviour. 
What, then, shall we understand by Spence’s phrase that 
instinct involves the performance of “certain actions” ? And 
how far shall we accept it ? We shall take it as implying so 
much definiteness of behaviour as renders instinctive acts sus- 
ceptible of scientific investigation, and in this sense shall 
accept it with some modification of phraseology. We shall 
freely admit, however, the existence of variations of instinctive 
behaviour analogous to variations in animal structure. It is 
the occurrence of such variations that renders the natural 
selection of instinctive modes of behaviour conceivable. We 
