Lynn Thorndike – Latin Treatises on Comets Between 1238 and 1368 A.D. – Albertus Magnus

8 September, 2017 - MA Coursework

Lynn Thorndike, Latin Treatises on Comets Between 1238 and 1368 A.D. (Chicago: Chgo UP, 1950).


Here in the third tractatus of his first book of meteorology, Albertus Magnus, aligning himself with Avicenna, Algazel, Ptolemy, among others, argues that a comet is “coarse terrestrial vapor, whose parts lie very close together, gradually rising from the lower part of the upper region of the air to its upper part, where it touches the concave surface of the sphere of fire and there is diffused and inflamed and so often seems long and diffuse.” For Albertus it is not only the authority of Avicenna, Algazel, and Ptolemy which supports this explanation of comets, but “reason,” or what might be called common sense, and observation by the senses: flame is simply kindled fumes; a comet is a sort of flame, “as is apparent to the sight;” therefore, it is kindled fumes. But this text is useful to historians not just for the theory of comets it espouses, but also those which it discards en route to its assertion.

Albertus begins by listing some then extant theories of comets: from Seneca and Apollonius, that comets are groups of several stars moving together in the lower spheres; that comets are stars nearly in conjunction, their quick succession giving the impression of a streak of light; from “certain pythagoreans among the Italian philosophers,” that a comet is vapor clinging to a planet; and, according to “some,” a comet is an illusion produced by the repeated reflection of its light among moist vapors, or that they are mirages of the effusions of different temperatures of humors rising from earth from different latitudes. A few of these theories had already been treated by Aristotle. Albertus must list a few more, just to be sure of his thoroughness – the authority of his claim, like that of all scholastic argumentation, rests in part on demonstrating that he has considered all others.

He deals with John of Damascus’s claim that comets were not part of the original creation but are instead ephemera whipped up to signify the deaths of kings and then dissolved away as quickly as they come. He deals with the claim of “certain learned moderns” that a comet is the impression left, like a scrape, of a planet against the boundary of the spheres of fire and air.  Another theory is somewhat confusing to me. Seneca, in his Natural Questions describes a comet as

. . . a star created together with the works of nature, whose nature it may be is ignored, yet that it is not transient fire is proved thus. Whatever things air produces are short-lived. How then can a comet last long in air, when air itself is not long permanent? For they are born in what is flighty and mobile, and it cannot be that fixed fire should have its seat and so pertinaciously adhere in a wandering body.


Seneca seems to me here not to be making a confident claim about the nature of comets so much as throwing his hands up at their paradoxical nature. They last too long in the sky to be transient fire (as from air), and yet fixed fire cannot have its seat and wander so. Thorndike identifies this to be a considerably altered translation on Albertus’s part and provides an alternate translation, but this does nothing to resolve the paradox. Perhaps you could help me understand this?

Having provided us with all the alternate theories of the nature of comets, Albertus must explain them away before he can establish the theory he shares with Avicenna, Algazel, and Ptolemy. The procedural and axiomatic bases on which Albertus discredits these alternate theories as invalid indirectly provide insight into those bases which were, conversely, valid to him. To the claim of some “moderns” that a comet is the scraping of a planet up against the boundaries of the spheres of air and fire, Albertus says that if this were the case, then comets would always be visible. This informs us of the contemporaneous understanding that the place of the planets was as the intersection of these spheres, or perhaps that the “moderns” making this claim were likewise challenging the traditionally-established position of the planets in the cosmological order (I do not know enough about the period to go further than this or to discount either of these possibilities – the point is that these are inferences that can be extracted from Albertus’s dismissals and the grounds on which he makes them). Albertus further denies any relationship between comets and the five planets because the planets pass through the zodiac “or very little outside” [of it], and yet we observe comets in all parts of the sky. This informs us that Albertus’s cosmological conception does not merely serve to save appearances, but is rooted in observable reality; we might also be enticed to ask, tangentially to the question of comets, what Albertus’s thoughts were as to the paths of the planets. Since he knows that they sometimes travel collinear with the zodiac, and sometimes only near it, that suggestion of irregularity might have shed light on other cosmological theories Albertus might have held (again, I do not know one way or the other, I am only generating potential lines of inquiry derivative from Albertus’s text).

It is worth pointing out Albertus’s refutation of one more of the theories of comets then under consideration: the idea that they signify wars or the deaths of potentates. Since Albertus has already established the view that comets are the slow conflagration of ascendant coarse vapors, he wonders how they can possibly relate to the onset of war or the end of a reign, since “vapor no more rises in a land where a pauper lives than where a rich man resides, whether he be king or someone else.” This reveals to us a naturalistic tendency in Albertus’s scholarship. Though he was (an eventually canonized) Dominican friar and bishop, Albertus does not hesitate to dismiss even a supernatural phenomenon on naturalistic grounds. He goes on to say that nor can there be a relationship between comets and wars or the death of kings on causal-logical grounds, since there have been comets without any wars or notable deaths, and vice versa.

Without going successively through each theory Albertus refuted in this text, it is clear the value in this hermeneutic exercise (for us in the present) lies not in ascertaining the “true reality,” for none of the theories Albertus explored bear any relation to what we currently understand of comets, but instead in what we can glean, both overtly and subtextually, from the  procedural and axiomatic bases Albert used to validate and invalidate competing explanations of phenomena.





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