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

by Lynn Thorndike

Some astrological technical detail.

In another treatise on how to predict the weather (De impressionibus aeris seu de prognosticatione[1454]) Grosseteste says that one must know such things as the powers of the signs and the natures of the planets.[1455] He then relates the four elements and four qualities to the planets and signs and proceeds to such further technical astrological terms as house, exaltation, triplicitas, terminus, facies, and aspect, and to an explanation of the effect of the eccentrics of the sun and moon upon inferior objects.[1456]

Man and the stars.

Grosseteste, like most of our Christian authors, exempts man in part by virtue of his free will and rational soul from the control of the stars. One of his brief fragments is entitled “That man is a microcosm” (Quod homo sit minor mundus), that is, a replica of the surrounding universe.[1457] One of his arguments for the finiteness of this world and of the stars is that all things are made for man and that when he no longer requires the processes of generation and corruption which the movements of the heavens cause, the heaven itself will cease to move and time will be no more.[1458] In a treatise on freedom of the will, he follows Augustine in The City of God in affirming that the rational soul is sublimer than the stars and in denying that all our actions which seem to be freely willed by us are predictable from the constellations, and that fate prevails as a necessity in all inferiors from the motion of the stars. He admits, however, that the human body is subject to two forces; as part of the world of cause it is changed in many ways by the movements of the stars, but it also is subject to the control of the mind especially in voluntary actions.

Grosseteste’s theory of comets.

Grosseteste has an ingenious theory which I do not remember having met elsewhere to explain why comets are signs of great disasters. In his treatise on comets he states that a comet is sublimated fire which has been separated from terrestrial nature and assimilated to celestial nature.[1459] The cause of this separation and assimilation by which comets are generated is the virtue of the heavenly bodies. Moreover, each comet has a particular star of its own which draws it as iron is drawn by adamant. This star, even if it is one of the fixed stars, must be related to one of the planets and hence the comet is under some planet also. Grosseteste then further explains that in every earthly object there are incorporated through the action of the celestial bodies particles of a more spiritual sort assimilated to the celestial natures. The generation of a comet, a process in which these fiery or ethereal particles are released from matter and carried up on high, is therefore the first step and sign of a more general release of the spiritual nature and of the consequent corruption of the terrestrial objects and compounds concerned, namely: in the first place, those under the rule of the same planet as the comet in question, and, in the second place, those in the region from which the comet was sublimated.[1460] But it is not easy to discern over which region the comet has especial significance of all those regions which are under the same parallel in which it appears, unless, concludes Grosseteste naïvely, it is that region where men are most alarmed by it.

Alchemy.

Grosseteste makes one or two incidental allusions to alchemy which show that he was a believer in the possibility of transmuting metals. He avers that nature intended that all metals should be gold, and that they vary from it only by degrees of imperfection.[1461] In another passage[1462] he mentions a theory of “the doctors of alchemy” that in each natural object there is, besides the four elements composing it, a fifth essence, unchangeable in itself but alterable after it has descended into inferior bodies. Here again we find a connection between alchemy and astrology.

Other treatises.

It is probable that not all of Grosseteste’s astrological writings are included in Baur’s edition. He mentions but does not publish a Digby manuscript and another of the thirteenth century in the Bibliothèque Nationale. Both are astronomical or astrological.[1463] A fourteenth century manuscript in the British Museum contains a treatise of “Grosthede” on the medicinal virtues of herbs.[1464] After the name of each herb the word “Grosthede” is usually added as if the items were extracts from a larger work. The treatise is not included in Baur’s edition and is perhaps spurious.