The seven regions of the air.
The discussion in the De natura rerum of the seven regions of the air and their humors, namely, dew, snow, hail, rain, “laudanum,” manna and honey, reminds one of Michael Scot’s treatment of the same subject,[1308] but seems to be drawn from a common source rather than directly copied from it. Thomas states that Aristotle has treated more fully of these humors in his Meteorology, but in reality Aristotle says nothing of the last three named in the Meteorology, although in the History of Animals he says that honey is distilled from the air by the stars. Thomas draws the same distinction as Michael Scot had made between natural honey and the artificial sort made by bees. He is willing to grant that the manna upon which the children of Israel lived was created in this region of the sky, although especially prepared for them by a divine miracle.
Astrological.
The astrological passages of the De natura rerum are neither striking nor novel. In his books on animals Thomas had stated that various animal substances such as the brains of wolves or the livers of mice vary in size with the waxing and waning of the moon. He denies that the planets possess sense or that their movements are voluntary, but he quotes Pliny’s statement that by the influence of Venus all things on earth are generated, and states the influence of each planet when it is in the ascendant. Under Mars men become choleric and bellicose. Jupiter is such a source of safety and good health that Martianus declared that were Jupiter the only planet, men would be immortal. Such, however, was not the Creator’s will. The word “Jupiter” is not without reason derived from iubens and pater, since during the ascension of this planet all terrestrial things are born. For unless seeds were severed from their beginnings by some occult virtue, they would always remain immovable in the state in which they were created. God accordingly put such power in the spheres of the stars and especially the planets that created things might obey his command to increase and multiply. They return, however, to the earth from which they came; the processes of nature are unceasingly repeated; and, as Solomon said, there is nothing new under the sun. Thomas therefore reaches the usual conclusion that except for human free will and special manifestations of divine will, all nature is placed by God under the rule of the stars. The influence of sun and moon is manifest, and “why should we not with entire reason believe the same of the other planets?”
Elements and spirits.
The nineteenth book opens with a discussion of the universe and creation and closes with a discussion of the four elements. Fire has eight effects expressed in the couplet:
Destruit, emollit, restringit, consolidatque;
Clarificat, terret, accendit, letificatque.
Thomas illustrates each of these effects by a verse of Scripture. Fire also has six properties, likewise expressed in a couplet:
Mobilis et siccus mundusque favilla tenetur;