426 Mental Factors in Evolution 



evolution rendered possible. Such is the logical outcome of Darwin's 

 teaching. 



Those who abide by the cardinal results of this teaching are 

 bound to regard all behaviour as the expression of the functional 

 activities of the living tissues of the organism, and all conscious 

 experience as correlated with such activities. For the purposes of 

 scientific treatment, mental processes are one mode of expression of 

 the same changes of which the physiological processes accompanying 

 behaviour are another mode of expression. This is simply accepted as 

 a fact which others may seek to explain. The behaviour itself is the 

 adaptive application of the energies of the organism ; it is called 

 forth by some form of presentation or stimulation brought to bear 

 on the organism by the environment. This presentation is always 

 an individual or personal matter. But in order that the organism 

 may be fitted to respond to the presentation of the environment it 

 must have undergone in some way a suitable preparation. According 

 to the theory of evolution this preparation is primarily racial and is 

 transmitted through heredity. Darwin's main thesis was that the 

 method of preparation is predominantly by natural selection. Sub- 

 ordinate to racial preparation, and always dependent thereon, is 

 individual or personal preparation through some kind of acquisition ; 

 of which the guidance of behaviour through individually won ex- 

 perience is a typical example. We here introduce the mental factor 

 because the facts seem to justify the inference. Thus there are some 

 modes of behaviour which are wholly and solely dependent upon 

 inherited racial preparation ; there are other modes of behaviour 

 which are also dependent, in part at least, on individual preparation. 

 In the former case the behaviour is adaptive on the first occurrence 

 of the appropriate presentation ; in the latter case accommodation 

 to circumstances is only reached after a greater or less amount of 

 acquired organic modification of structure, often accompanied (as 

 we assume) in the higher animals by acquired experience. Logically 

 and biologically the two classes of behaviour are clearly distinguish- 

 able : but the analysis of complex cases of behaviour where the two 

 factors cooperate, is difficult and requires careful and critical study 

 of life-history. 



The foundations of the mental life are laid in the conscious 

 experience that accompanies those modes of behaviour, dependent 

 entirely on racial preparation, which may broadly be described as 

 instinctive. In the eighth chapter of The Origin of Species Darwin 

 says 1 , "I will not attempt any definition of instinct.... Every one 

 understands what is meant, when it is said that instinct impels the 

 cuckoo to migrate and to lay her eggs in other birds' nests. An 



1 Origin of Species (6th edit.), p. 205. 



