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

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Response

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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Notes

• 62 – Seneca & Apollonius– comets are groups of several stars moving together, gathered in the lower spheres – mobile like the planets and not fixed like the stars in the 8th sphere
• 63 – Seneca & Apollonius – called stars nearly in conjunction comets because their being lined up gives the impression of a streak of light
• Certain pythagoreans among the Italian philosophers said a comet is vapor clinging to a planet
• 64 – according to some the tail of a comet is an illusion of the repeated reflection of its light among moist vapors
• 64-5 – another “false” view of comets is that their tails are illusions cause by the effusions of different temperatures of humors from different latitudes on earth
• 65 – Aristotle lists all these to dismiss them
• Albertus wants to list a few more theories, not mentioned and dismissed by Aristotle so as to dismiss them himself – from Seneca and John of Damascus
• John of Damascus – comets were not part of the original creation but were created in the moment to signify the deaths of kings and are dissolved after serving their purpose
• Seneca – comets must be short-lived because they are produced by air, because air itself is not long permanent. It cannot be that fixed fire should have its seat and so pertinaciously adhere in a wandering body. – thus it cannot be transient fire
  • This is confusing, perhaps ask Dr. Vermij for clarification??
• 65-6 – Certain “moderns” say a comet is the impression of one of the five plants at the meeting line of fire and air where the convex surface of the air mingles with the concave of fire – for there are certain obscure lines of air and certain luminous, as they say, lines of fire which are further illuminated by the light descending from one of the five plants, and so the tail seems to them to be made up of obscure lines and luminous lines intermixed
• 66 – the four arguments for the above theory
• 67 – “the correct views of physicists, Avicenna, Algazel, Ptolemy, and many others, as to comets, who all agree on the same point”

 

• “I say, then, that a comet is nothing else than coarse terrestrial vapor, who 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. I say “terrestrial vapor” to denote the material of the vapor. And I say “coarse” because, if it were subtle, it would quickly evaporate and be dissipated. And I say “whose parts are close together,” since it is well mixed and viscous in so far as such vapor which is not actually humid and viscous can be. And it is said “ascend gradually,” since in rain-producing vapors are intermingled some ignited terrestrial parts which do not all descend with the rain, and those which do descend for the most part reascend with evaporation. And they escape beyond the middle cold region of the air because of their state and stay there and multiply.”

• 68 – “Moreover, that it is so, testify the illustrious philosophers Avicenna and Algazel. For Avicenna speaks thus: “A star which is called tailed is made of thick ignited fumes, which, since it is quickly converted, sometimes revolves circularly with the sphere of fire.”

• 69 – “Reason, too, rallies to the support of this opinion, since it is evident that flame is nothing but kindled fumes; now a comet is a sort of flame, as is apparent to the sight; therefore, it is kindled fumes.”

• “Besides, let us ask our modern doctors, since a comet is light kindled by one of the five planets at the boundary of air and fire [according to them]and since the planets always are moved above this kind of boundary where air is mixed with fire, why don’t comets always appear? Also why don’t several comets appear at the same time, since several planets may rise simultaneously above this mixture of air and fire?”

• 70 – “Furthermore, if a comet is always produced by one of the five planets, then it should never be seen outside the path of the planets. But the path of the planets is in the zodiac or very little outside; therefore, a comet should always be seen in the zodiac or near it; and yet this is false, since Aristotle says that we see comets to the north and south and in every part of the sky.”

• Seneca must be wrong because comets vanish before setting over the horizon line, thus the must be corruptible and extinguishable – cannot be fixed fire

• 70-1 – John of Damascus probably isn’t correct in asserting that a comet is god making a new temporary star because why should he make them in different figures and colors?

• 71-2 – The opinion of Apollonius that a comet is a conjunction of planets can’t be true on four grounds

• 73 – A Digression Explaining Why There Are Said To Be Five Comets and No More

• 74 – “. . . five comets are not reckoned as five planets, as we will state below, but either according to five differences of the vapor composing them or according to five forms of stars having tails.”

• Basically that there are two essential qualities of vapor, coarse and subtle, so these are two types of comets. With any two types, there is also an equal mixture of the two (a third type of comet) and an equal mixture of this middle composition and each of the two extremes, coarse and subtle (the fourth and fifth types of comets)

• Also five “by figure” – vapor surrounds “it” in a circuit, above it, below it, or to the left or right – what is the “it” according to Albertus?

• 75 – A DIGRESSION WHY COMETS SIGNIFY THE DEATH OF POTENTATES AND WARS

• “The reason is not apparent, 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 is indicative of a naturalistic explanation for a seemingly supernatural phenomenon. Albertus is considering, if comets signify the deaths of ‘magnates’ it would seem to be a result of some effect of the magnate on the vapor in his vicinity

• “Furthermore, it is evident that a comet has a natural cause not dependent on anything else; so it seems that it has no relation to someone’s death or to war. For if it be said that it does relate to war or someone’s death, either it does so as cause or effect or sign.”

• “Evidently it does not have sufficient relation to anything as cause, since it is neither efficient cause, nor formal, nor final, nor material. Similarly it is proved not to be an effect, since neither necessarily follows the other, but an effect necessarily follows its cause. Nor does it relate even as a sign, since it has not conformity, but every sign has conformity with what it signifies.”

• So it can’t be effect or sign because there is no consistent correlation between deaths and wars, on the one hand, and the presence of comets. Important people die and wars are fought all the time without a comet showing up. On the reverse, you could probably always find an example of a death or a war whenever a comet shows up, but this can be explained away as coincidence.