Astrology
Astrology was also an important branch of occult study with the Moors of Spain, whose consideration of it greatly assisted the science of mathematics, especially that branch of it which still retains its Arabic name—algebra (al = the, jabara = to set, compute). It is probable that the Arabs first received an insight into the practice of foretelling events by the position of the planets at a given time from the Chaldeans, who undoubtedly were its earliest students. References to astrology are plentifully encountered in Spanish story, as the reader will have observed. But high as it stood in the estimation of the Moorish sages, it was still subservient to the grander and more mysterious art of magic, whereby the spirits of the air could be forced to do the will of the magus, and carry out his behests in four elements. Most unfortunately, we are almost entirely ignorant of the tenets of Moorish magic, owing probably to the circumstance that it was averse to the spirit of Islam. But we know that it was founded upon Alexandrian magic, and therefore recognized the principles of that art as laid down by the great Hermes Trismegistus, who was none other than the Egyptian Thoth, the god of writing, computation, and wisdom.
About the end of the tenth century the learned men of Europe began to resort to Spain for the purpose of studying the arts, occult and otherwise. Among the first to do so was Gerbert, afterward Pope Sylvester II, who spent several years in Cordova, and who introduced into Christendom the knowledge of the Arabic numerals and the no less useful art of clock-making. Strange that he did not apply his knowledge of the one to the other, and that even to-day our timepieces are burdened with the old and cumbrous Roman numerals! William of Malmesbury assures us that Gerbert made many discoveries of treasure through the art of necromancy, and relates how he visited a magnificent subterranean palace, which, though dazzling to the sight, would not remain when its splendours were subjected to the test of human touch. Ignorant Europe took Gerbert’s mathematical diagrams for magical signs, and his occult reputation increased as his moral character withered. It was said that the Devil had promised him that he should not die until he had celebrated high mass at Jerusalem. One day Gerbert celebrated his office in the Church of the Holy Cross of Jerusalem at Rome, and, feeling ill, asked where he was, observed the double entendre of the Evil One, and expired. Such was the tale that benighted ignorance cast round the memory of this single-minded and enlightened man, much in the same spirit as it bedevilled the recollections of our own Michael Scot and Roger Bacon.