18 BIOLOGY AND ITS MAKERS 
while metaphysical speculation became the dominant form 
of mental activity. 
Authority Declared the Source of Knowledge.—In this 
atmosphere controversies over trivial points were engendered, 
and the ancient writings were quoted as sustaining one side 
or the other. All this led to the referring of questions as to 
their truth or error to authority as the source of knowledge, 
and resulted in a complete eclipse of reason. Amusing illus- 
trations of the situation are abundant; as when, in the 
Middle Ages, the question of the number of teeth in the horse 
was debated with great heat in many contentious writings. 
Apparently none of the contestants thought of the simple 
expedient of counting them, but tried only to sustain their 
position by reference to authority. Again, one who noticed 
spots on the sun became convinced of the error of his eyes 
because Aristotle had somewhere written ‘‘The face of the 
sun is immaculate.” 
This was a barren period not only for science, but also 
for ecclesiastical advance. Notwithstanding the fact that 
for more than a thousand years the only new works were 
written by professional theologians, there was no substantial 
advance in their field, and we cannot escape the reflection 
that the reciprocal action of free inquiry is essential to the 
growth of theology as of other departments of learning. 
In the period from the downfall of Rome to the revival 
of learning, one eminent theologian, St. Augustine, stands 
in relief for the openness of his mind to new truth and for 
his expressions upon the relation of revelation in the Scrip- 
tures to the observation of nature. His position will be more 
clearly indicated in the chapter dealing with the rise of 
evolutionary thought. 
Perhaps it has been the disposition of historians to paint 
the Middle Ages in too dark colors in order to provide a 
background on which fitly to portray the subsequent awak- 
