Such occult virtue, or at least the “specific form” upon which it partly depends, is ascribed by Arnald as usual to the influence of the stars. It is owing, for example, to “the specific influence of the heavens” that gold is “something arcane, most perfect in its equable temperament, composed of a marvelous proportion of the virtues of the elements, and which has not its like among compounds.”[2705] The gold made by alchemists may resemble it in color and substance but not in this occult virtue. Arnald, indeed, holds what Aquinas and others denied, that different individuals of the same species may be endowed by the stars with diverse properties.[2706] This is in his opinion the explanation why one sapphire will harm and another cleanse the human eye. “It leaps into the eye and is received in its bosom without injury and comes out loaded with foreign matter.”
Astrological medicine.
From the occult virtue of terrestrial objects we are thus led as usual to the superior influence of the stars, which occupies a prominent, or better, fundamental place in Arnald’s works. He affirms that “since it is evident that God, the supreme artificer and begetter, has committed the government of nature to the motions of the stars, their influence upon the human body is no slight one.”[2707] Or he cites Galen as saying that philosophers assert that all things on earth are formed and fulfilled by the course and working of the heavenly bodies.[2708] The hour of collecting medicines is often very important[2709] and the physician should also know how the air about us is altered by the stars.[2710] Astrological medicine is also found in Arnald’s treatise on preserving youth and retarding age,[2711] and in his Judgments of Infirmities by the Motion of the Planets, where he also associates the members of the human body with the signs of the zodiac. This he does for the seven planets in his treatise on epilepsy.[2712]
Bleeding and the moon.
Arnald alludes a number of times to the practice of bleeding according to the phases of the moon. In his Regulation of Health he discusses how the age of the moon and its location, conjunctions, and aspects must be taken into account.[2713] In his General Rules for the Cure of Disease[2714] he says that the influence of the moon should be regarded by physicians in their pharmacy as well as their blood-letting, as anyone who operates long and intelligently will find by experience. Astrological authors prove it, but medical authors generally remain silent on this point. Arnald finds support, however, in Galen’s Critical Days and other works, and in the more recent works of Gilbert of England, who cautions to observe the moon in bleeding and advises against blood-letting in dog-days or on Egyptian days. Arnald would also include cauterization, other surgical operations, and the administration of drugs, and there is much observance of dog-days in his Treatise against the stone. On the other hand, Arnald rejects as false and worthless the statement in the Regimen Salernitanum that the months of April, May, and September are lunar and that in them are the days on which bleeding is prohibited.
Bernard Gordon’s personal experience.
Bernard Gordon, a medical contemporary of Arnald, notes in his Phlebotomy, written in 1307, that wise astronomers agree that bleeding should not be practiced when the moon is in Gemini, because at that time the vein will not give blood or it will open again or the patient will die. He goes on to narrate, however, that once having made all preparations to bleed himself, it suddenly occurred to him that the moon was then in Gemini. He persisted with the operation, however, which would seem to indicate that he did not really believe that it would prove disastrous; and he records that as a matter of fact that particular bleeding did him more good than any other one he ever underwent. Yet as the Histoire Littéraire notes,[2715] he reproduced the opinion of the astronomers without comment in his Prognostications. Which suggests that clergy who practiced in private arts of divination which they condemned in their writings were not the only ones whose preaching and practice might be divergent; Bernard defies astrological medicine successfully in personal practice but he continues to preach it in his writings. But to return to Arnald.
Operative astrology or magic.
Arnald believes that a human operator can accomplish great things by availing himself of the influences of the stars, an idea which he develops especially in the treatise entitled, De parte operativa. In the first place, there is the negative consideration that the force which pours forth unceasingly from the stars is not absorbed unless bodies are in a condition to receive it, and that they may be put into such a favorable condition by art as well as by nature. More positively, everything produced by art or nature receives from the sky some property of acting upon other bodies or of being acted upon by them. So any man who knows the influences of the stars and how to prepare objects to receive them, can produce great and marvelous changes in inferior things. Arnald thinks that “the juggleries of the magicians and the illusions of the enchanters” and the operations of sorcerers and those who fascinate, have efficacy in no other way, except of course as demons may lend their aid. In other words, astrology is the basis of magic.
Seals or images.