BIOLOGICAL EVOLUTION 77 
natural selection in the struggle between individuals where Dar- 
win laid chief emphasis.! 
There seems to be a strong tendency now to accept the theory 
of mutations in the line of inheritable unit characters, to empha- 
size the unity of the species in the struggle for existence and to 
rate highly the importance of geographical isolation in the 
formation of new species and ethnic groups. There seems to be 
a tendency in certain quarters, also, following the lead of Nageli 
and Driesch, to return to the hyper-scientific method of earlier 
days and posit a life principle or force as the mainspring of 
development. This is strongly opposed, however, by those who 
hold that science is weakened just in proportion as it gets beyond 
the domain of demonstrable facts, so on the whole sociology can 
claim little support for this theory from biologists of recognized 
authority.? 
Most clear and certain of all, it would seem, stands out above 
the confusion of present biological knowledge and hypotheses the 
doctrine of adaptation though with differences of interpretation 
and emphasis. In proportion as the struggle is between individ- 
uals, either friends or foes, the weak and otherwise less adapted 
tend to be eliminated, but in proportion as the struggle is between 
groups certain instincts seem to have been evolved which have as 
their specific function the strengthening of the group in collective 
activity. Some of these instincts seem to work for the detriment 
of the individual member who does not fit in with the “ group 
sentiment of safety’? or whose death will in some way be 
advantageous to the group as in the destruction of the weak, the 
’ For a sane criticism of Darwinism, see Kellogg, Darwinism To-day, chs. III, 
TV, V. 
2 Although this theory is in general repudiated as extra-scientific and tending 
to turn scientists aside from their supreme task of finding out the efficient causes 
of change, the vast realm of mystery that still baffles biologists in their endeavor 
to explain the process of biological evolution and has led some to posit a force or 
intelligence as the cause of these changes, gives a vantage ground for social phi- 
losophers who are not limited, as are scientists, to mere description in terms of co- 
existence and sequence, but have as their task to push their investigations and 
formulations on to an underlying or final cause as have Ratzenhofer, Fiske, and 
Ward. Cf. Kellogg, op. cit., pp. 226 f. 
3 Ward, Pure Sociology, pp. 134, 419. 
