A History of Magic and Experimental Science, Volume 2 (of 2) / During the First Thirteen Centuries of Our Era

by Lynn Thorndike

Transmission of Arabic astrology.

Throughout the twelfth century from its first years to its close may be traced the transit of learning from the Arabic world, and more particularly from the Spanish peninsula, to northwestern Europe. Three points may be made concerning this transmission: it involves Latin translation from the Arabic; the matter translated is largely mathematical, or more especially astronomical and astrological in character; finally, it is often experimental.

Walcher, prior of Malvern.

On the very threshold of the twelfth century, in addition to Adelard of Bath to whom we have given a separate chapter, we meet with another Englishman, Walcher, prior of Malvern, whom we find associated with Peter Alphonso or Pedro Alfonso, who apparently was a converted Spanish Jew. Walcher’s experimental observations would seem to have antedated his association with Pedro, since a chapter headed, “Of the writer’s experience,”[160] in lunar tables which he composed between 1107 and 1112, tells of an eclipse which he saw in Italy in 1091 but could not observe exactly because he had no clock (horologium) at hand to measure the time, and of another in the succeeding year after his return to England which he was able to observe more scientifically with the aid of an astrolabe. In 1120 Walcher translated into Latin, at least according to the testimony of the manuscripts, an astronomical work by Pedro Alfonso on the Dragon.[161] Pedro perhaps wrote the original in Hebrew or Spanish or translated it from the Arabic into one of those languages, but we also know of his writing in Latin himself.

Pedro Alfonso.

This Pedro Alfonso seems to have been the same[162] who in 1106 in his forty-fourth year was baptized at Huesca with the name of his godfather, King Alfonso I of Aragon, and who wrote the Disciplina clericalis and Dialogi cum Iudeo. Indeed we find the Disciplina clericalis and De dracone ascribed to him in the same manuscript.[163] In another manuscript chronological and astronomical tables are found under his name and the accompanying explanatory text opens, “Said Pedro Alfonso, servant of Jesus Christ and translator of this book.”[164] This expression is very similar, as Haskins has pointed out, to a heading in a manuscript of the Disciplina clericalis, “Said Pedro Alfonso, servant of Christ Jesus, physician of Henry the first (sic) king of the Angles, composer of this book.”[165] The experimental pretensions and astrological leanings of the astronomical treatise are suggested by Pedro’s statement that the science of the stars divides into three parts, marvelous in reasoning, notable in the signification of events, and approved in experience; and that the third part is the science of the nature of the spheres and stars, and their significations in earthly affairs which happen from the virtue of their nature and the diversity of their movements, things known by experiment.

His letter to the Peripatetics.

In a manuscript at the British Museum[166] I have read what seems to be a third astronomical treatise by Pedro Alfonso, differing both from the preceding and from the De dracone.[167] We meet as before the expression, “Said Alfonso, servant of Jesus Christ and translator of this book,”[168] and the emphasis upon experiment and astrology continues. It will be noted further that in this treatise, which takes the form of a letter to Peripatetics and those nourished by the milk of philosophy everywhere through France, Pedro is no longer connected with Englishmen, although this manuscript, too, is in an English library. After rehearsing the utility of grammar, dialectic, and arithmetic, Pedro finally comes to astronomy, an art with which “all of the Latins generally” are little acquainted, in which he himself has long been occupied, and a portion of which he presents to them as something rare and precious. It has come to his ears that some seekers after wisdom are preparing to traverse distant provinces and penetrate to remote regions in order to acquire fuller astronomical knowledge, and he proposes to save them from this inconvenience by bringing astronomy to them. Apparently, therefore, this letter to the Peripatetics and other students of philosophy is simply the advertisement of, or preface to, a translation by Pedro of some astronomical or astrological work, presumably from the Arabic.[169] It is accordingly mainly devoted to a justification of the thorough study of astronomy and astrology. Many persons, in Pedro’s opinion, are simply too lazy to take the trouble to ground themselves properly therein. Those who think they know all about the subject because they have read Macrobius and a few other authors are found wanting in a crisis,—a passage meant doubtless as a hit at those who base their knowledge of astronomy simply upon Latin authors. Pedro also alludes to those who have been accustomed to regard themselves as teachers of astronomy and now hate to turn pupils again.

Experimental method.

The contrast which Pedro draws, however, is not so much between Latin and Arabic writings as it is between dependence upon a few past authorities and adoption of the experimental method. He argues that the principles of astronomy were discovered in the first place only through experimentation, and that today no one can understand the art fundamentally without actual observation and experience. He believes that astrology as well as astronomy is proved by experience. “It has been proved therefore by experimental argument that we can truly affirm that the sun and moon and other planets exert their influences in earthly affairs.”[170] Or, as he says in another passage, “And indeed many other innumerable things happen on earth in accordance with the courses of the stars, and pass unnoticed by the senses of most men, but are discovered and understood by the subtle acumen of learned men who are skilled in this art.”[171] Pedro’s letter further includes some astrological medicine, interesting in connection with the statement in another manuscript that he was the physician of Henry I of England. In this context, too, he shows familiarity with the translations from the Arabic of Constantinus Africanus.[172]