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had written on nature rather than to a study of nature 
itself. 
Science in the middle ages was fostered chiefly by the 
Arabs who believed in the pseudo-sciences of astrology and 
alchemy, but they did much to advance algebra and some 
of the sciences. By the end of the 14th century astrology 
reached the summit of its popularity. At this time every- 
thing that happened on the earth was attributed to the 
condition and position of the stars. Disease, weather, crop 
growth, and even personal fortune or misfortune were 
thought to be profoundly, if not completely, dependent on 
heavenly bodies. Man was in no sense thought to be mas- 
ter; he was considered to be merely a victim of the 
stars. 
Tradition, belief in authority, and superstitions of the 
false sciences of astrology and alchemy long and successfully 
resisted the advance of knowledge. Time-honored ideas, 
nevertheless, received a rude shock at the hands of Coper- 
nicus (1473) and by 1600, when Giordano Bruno was 
burned at the stake, the germ of original investigation had 
been planted. In the next century perhaps the greatest 
revolution in thought that has occurred in all history swept 
the western world. To this many factors contributed: the 
genius of a few great men like Newton, Galileo, Harvey, 
Kepler, Descartes, Bacon, and Leibnitz; the invention of 
the telescope and the compound microscope; and the general 
awakening of thought by the Renaissance. 
Before Galileo, only two modern men of science are 
conspicuous: Copernicus, who studied the movements of 
heavenly bodies, and Vesalius (1514-1564) who overthrew 
the authority of Galen and studied at first hand the organ- 
ization of the human body. Not until the seventeenth cen- 
tury did modern science gain a secure footing. In 1628 
William Harvey, by adding experiment to observation, 
demonstrated the circulation of the blood and created a 
new physiology, and in 1687 Newton published his “Prin- 
cipia” which established the science of mechanics. These 
two contributions were so revolutionary that the earlier 
ideas of physical and biological science were almost com- 
