Facio Cardano
(1444-1524), a learned jurist of Milan, himself distinguished by a taste
for mathematics. He was educated at the university of Pavia, and
subsequently at that of Padua, where he graduated in medicine. He was,
however, excluded from the College of Physicians at Milan on account of
his illegitimate birth, and it is not surprising that his first book
should have been an exposure of the fallacies of the faculty. A
fortunate cure of the child of the Milanese senator Sfondrato now
brought him into notice, and the interest of his patron procured him
admission into the medical body. About this time (1539) he obtained
additional celebrity by the publication of his _Practica arithmeticae
generalis_, a work of great merit for the time, and he became engaged
in a correspondence with Niccolo Tartaglia, who had discovered a
solution of cubic equations. This discovery Tartaglia had kept to
himself, but he was ultimately induced to communicate it to Cardan under
a solemn promise that it should never be divulged. Cardan, however,
published it in his comprehensive treatise on algebra (_Artis magnae
sive de regulis Algebrae liber unus_) which appeared at Nuremberg in
1545 (see ALGEBRA: _History_). Two years previously he had published a
work even more highly regarded by his contemporaries, his celebrated
treatise on astrology. As a believer in astrology Cardan was on a level
with the best minds of his age; the distinction consisted in the
comparatively cautious spirit of his inquiries and his disposition to
confirm his assertions by an appeal to facts, or what he believed to be
such. A very considerable part of his treatise is based upon
observations carefully collected by himself, and seemingly well
calculated to support his theories so far as they extend. Numerous
instances of his belief in dreams and omens may be collected from his
writings, and he especially valued himself on being one of the five or
six celebrated men to whom, as to Socrates, had been vouchsafed the
assistance of a guardian daemon.

In 1547 he was appointed professor of medicine at Pavia. The publication
of his works on algebra and astrology at this juncture had gained for
him a European renown, and procured him flattering offers from Pope Paul
III. and the king of Denmark, both of which he declined. In 1551 his
reputation was crowned by the publication of his great work, _De
Subtilitate Rerum_, which embodied the soundest physical learning of his
time