442 Mental Factors in Evolution 
There are diversities of opinion, as Darwin showed, with regard 
to the range of instinct in man and the higher animals as contrasted 
with lower types. Darwin himself said? that “Man, perhaps, has 
somewhat fewer instincts than those possessed by the animals which 
come next to him in the series.” On the other hand, Prof. Wm. James 
says? that man is probably the animal with most instincts. The true 
position is that man and the higher animals have fewer complete and 
self-sufficing instincts than those which stand lower in the scale of 
mental evolution, but that they have an equally large or perhaps 
larger mass of instinctive raw material which may furnish the stuff 
to be elaborated by intelligent processes. There is, perhaps, a greater 
abundance of the primary tissue of experience to be refashioned and 
integrated by secondary modification; there is probably the same 
differentiation in relation to the determining biological ends, but 
there is at the outset less differentiation of the particular and specific 
modes of behaviour. The specialised instinctive performances and 
their concomitant experience-complexes are at the outset more 
indefinite. Only through acquired connections, correlated with 
experience, do they become definitely organised. 
The full working-out of the delicate and subtle relationship of 
instinct and educability—that is, of the hereditary and the acquired 
factors in the mental life—is the task which lies before genetic and 
comparative psychology. They interact throughout the whole of 
life, and their interactions are very complex. No one can read the 
chapters of The Descent of Man which Darwin devotes to a con- 
sideration of the mental characters of man and animals without 
noticing, on the one hand, how sedulous he is in his search for 
hereditary foundations, and, on the other hand, how fully he realises 
the importance of acquired habits of mind. The fact that educability 
itself has innate tendencies—is in fact a partially differentiated 
educability—renders the unravelling of the factors of mental progress 
all the more difficult. 
In his comparison of the mental powers of men and animals it 
was essential that Darwin should lay stress on points of similarity 
rather than on points of difference. Seeking to establish a doctrine 
of evolution, with its basal concept of continuity of process and 
community of character, he was bound to render clear and to em- 
phasise the contention that the difference in mind between man and 
the higher animals, great as it is, is one of degree and not of kind. 
To this end Darwin not only recorded a large number of valuable 
observations of his own, and collected a considerable body of informa- 
tion from reliable sources, he presented the whole subject in a new 
light and showed that a natural history of mind might be written 
1 Descent of Man, Vol. 1. p. 100. 2 Principles of Psychology, Vol. 11. p. 289. 
