OUTLINE OF BIOLOGICAL PROGRESS IQ 
ening. It was a remolding period through which it was 
necessary to pass after the overthrow of ancient civilization 
and the mixture of the less advanced people of the North with 
those of the South. The opportunities for advance were 
greatly circumscribed; the scarcity of books and the lack of 
facilities for travel prevented any general dissemination of 
learning, while the irresponsible method of the time, of 
appealing to authority on all questions, threw a barrier across 
the stream of progress. Intellectuality was not, however, 
entirely crushed during the prevalence of these conditions. 
The medieval philosophers were masters of the metaphysical 
method of argument, and their mentality was by no means 
dull. While some branches of learning might make a little 
advance, the study of nature suffered the most, for the knowl- 
edge of natural phenomena necessitates a mind turned 
outward in direct observation of the phenomena of the 
natural and physical universe. 
Renewal of Observation.—It was an epoch of great im- 
portance, therefore, when men began again to observe, and 
to attempt, even in an unskilful way, hampered by intellec- 
tual inheritance and habit, to unravel the mysteries of nature 
and to trace the relation between causes and effects in the 
universe. This new movement was a revolt of the intellect 
against existing conditions. In it were locked up all the 
benefits that have accrued from the development of modern 
science. Just as the decline had been due to many causes, 
so also the general revival was complex. The invention of 
printing, the voyages of mariners, the rise of universities, 
and the circulation of ideas consequent upon the Crusades, 
all helped to disseminate the intellectual ferment. These 
generic influences aided in molding the environment, but, 
just as the pause in science had been due to the turning away 
from nature and to new mental interests, so the revival was 
a return to nature and to the method of science. The pio- 
