OUTLINE OF BIOLOGICAL PROGRESS 19 



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- 



