74 Proceedings of Royal Society of Edinburgh. [sess. 
action is the constant attendant of vital action, and is the true 
explanation of it, we transform the theory of existence so as to 
represent it as a single life history, unfolding itself more fully as the 
ages roll on, — moving through matter, and next through spirit, hack 
to the Idea, as Hegel represents. But the scientific conception 
makes intelligence a later type of being, evolved in the history of 
organic advance. In this light we read the theory of evolution. 
We are therefore required to concentrate attention on the classifi- 
cation of the higher animals already given, so as to trace the appear- 
ance of intelligence in our world’s history. As we contemplate 
these higher animals, first in their relation to lower orders of life, 
and next in their relation to man, it seems plain that we have to 
deal with three sets of facts, — sensori-motor activity in the simpler 
organic forms; a simpler or lower order of intelligence, as in the 
dog; and a higher intelligence, in possession of man. It would 
seem that no scheme of natural history can meet requirements, if it 
fail to make account of these three stages of life, or three distinct 
sets of facts. 
The recognition of this sufficiently clears the path, carrying us 
forward to the highest form of the problem, concerning man’s place 
in nature, without our being entangled and delayed with the question 
concerning animal intelligence. Our own intelligence, as the better 
known to us and the more easily studied, can supply the essential 
phases of this problem, and can be discussed without prejudice to 
the intervening and lower type of intelligence. The problem is 
clear and definite, — How can sensori-motor action evolve a rational 
activity ? Or, taking the problem, in the first instance, on the side 
of intelligence alone, — How can nerve sensibility provide for evolu- 
tion of intelligence ? That this has been matter of actual history is 
fast becoming the traditional belief of thorough-going evolutionists. 
Scientific tests, therefore, need to be applied with exactness here, 
seeking for facts and their interpretation. 
Given a highly-developed organism, with large adaptation to 
environment, and modified under loDg application of the law of here- 
dity, to account for the rise of intelligence as exercised by man. The 
problem is certainly not an easy one, though the popular scientific 
faith shows no sign of misgiving. Accepting all the conditions as 
laid down by the evolutionist, there still seems a set of difficulties 
