lxxiv REPORT—1874. 
Whewell the Arab elements in our scientific terms, and points out that the 
under garment of ladies retains to this hourits Arabname. He gives examples 
of what Arabian men of science accomplished, dwelling particularly on Alhazen, 
who was the first to correct the Platonic notion that rays of light are emitted 
by the eye. He discovered atmospheric refraction, and points out that we 
sec the sun and the moon after they have set. He explains the enlargement of 
the sun and moon, and the shortening of the vertical diameters of both 
these bodies, when near the horizon. He is aware that the atmosphere 
decreases in density with increase of elevation, and actually fixes its height at 
58 miles. In the Book of the Balance Wisdom, he sets forth the connexion 
between the weight of the atmosphere and its increasing density. He shows 
that a body’ will weigh differently in a rare and dense atmosphere: he 
considers the force with which plunged bodies rise through heavier media. 
He understands the doctrine of the centre of gravity, and applies it to the inves- 
tigation of balances and steelyards. He recognizes gravity as a force, though he 
falls into the error of making it diminish simply as the distance increased, and of 
making it purely terrestrial. He knows the relation between the velocities, 
spaces, and times of falling bodies, and has distinct ideas of capillary attrac- 
tion. He improved the hydrometer. The determination of the densities of 
bodies as given by Alhazen approach very closely to our own. ‘I join,” 
says Draper, in the pious prayer of Alhazen, “that in the day of judgment 
the All-Merciful will take pity on the soul of Abur-Raihan, because he was 
the first of the race of men to construct a table of specific gravities.” If all 
this be historic truth (and I have entire confidence in Dr. Draper), well may 
he “deplore the systematic manner in which the literature of Europe has 
contrived to put out of sight our scientific obligations to the Mahomme- 
dans??*, . 
The strain upon the mind during the stationary period towards ultra- 
terrestrial things to the neglect of problems close at hand, was sure to 
provoke reaction. But the reaction was gradual; for the ground was 
dangerous, a power being at hand competent to crush the critic who went too 
far. To elude this power and still allow opportunity for the expression of 
opinion, the doctrine of “ twofold truth” was invented, according to which an 
opinion might be held “ theologically,” and the opposite opinion “ philoso- 
phically”?. Thus, in the thirteenth century, the creation of the world in six 
days, and the unchangeableness of the individual soul, which had been so di- 
stinctly affirmed by St. Thomas Aquinas, were both denied philosophically, 
but admitted to be true as articles of the Catholic faith. When Protagoras 
uttered the maxim which brought upon him so much yituperation, that 
“ opposite assertions are equally true,” he simply meant that human beings 
differed so much from each other that what was subjectively true to the one 
might be subjectively untrue to the other. The great Sophist never meant 
to play fast and loose with the truth by saying that one of two opposite 
assertions, made by the same individual, could possibly escape being a lie. 
Tt was not “sophistry,” but the dread of theologic vengeance that generated 
this double dealing with conviction; and it is astonishing to notice what 
lengths were possible to men who were adroit in the use of artifices of this 
kind. 
Towards the close of the stationary period a word-weariness, if I may so 
express it, took more and more possession of men’s minds. Christendom had 
become sick of the School philosophy and its verbal wastes, which led to no 
* Intellectual Development of Europe, p. 359. 
t Lange, 2nd edit. pp. 181, 182, 
