72 
Proceedings of Royal Society of Edinburgh. [sess. 
needful for securing results. Granting, as a hypothesis, biological 
evolution under the conditions stated, with reservation of all the 
open problems concerned with the history of evolution, the way is 
clear for considering how this theory of evolution stands related to 
man’s place in nature. 
While discussing the question from the standpoint of evolution, 
we must accept Herbert Spencer’s view as correct, which takes 
evolution of existence as a whole as indicating the true range of the 
problem raised. “ Evolution becomes not one in principle only, hut 
one in fact,” implying “ one evolution going on everywhere after the 
same manner.” Further, we take it as beyond question that man 
belongs to Nature, and in respect of his whole being comes within 
the scope of science. An evolution theory must include man, or 
acknowledge that it is not a theory of existence as a whole. The 
position of the theory and of all scientific observers devoted to it 
is clear. Every piece of scientific work, whether concerned with 
structure of organism, with functional activity, with visible adapta- 
tions of organism, or with manifestations of animal intelligence, is 
an essential contribution towards solution of our problem. On the 
other hand, everything which tends to clear up the specialties of 
human life, whether concerned with the structure and functions of 
human organism, or with the activities of human intelligence as 
these are concerned .with the attainment of scientific knowledge 
and the government of conduct, is a definite contribution towards 
the scientific conclusion we seek to reach. The outstanding problem 
is this, — What is man’s place in nature ? 
Scientific inquiry advances towards this problem along the path- 
way of biological research, always making account of the common 
characteristics of life. The common condition of organic existence, 
from the lowest form to the highest, is the sensori-motor nerve- 
system. The main question is therefore definitely shaped, — What is 
a sensori-motor system equal to-? How much can be scientifically 
made out as lying within range of such a system when highly 
differentiated and co-ordinated in an elaborate nerve-centre, or 
series of nerve-centres, liable to modification in the history of its 
* 
activity ? According to the answer to this inquiry is the advance 
made towards including man within a science of nature. 
The laws of a sensori-motor system, as it provides for the activity 
