To understand which we must turn to the oft-quoted fourteenth chapter of the second treatise in the Convivio. Here we find that Jupiter “moves between two heavens” which “are antagonistic to its excellent temperateness, that is to say the heavens of Mars and that of Saturn,”[685] and Dante quotes Ptolemy as saying that Jupiter is a star of temperate constitution, between the cold of Saturn and the heat of Mars.
It seems that these ideas of cold and heat, as applied to the planets, were taken literally, not merely as poetical descriptions of colour, nor of astrological significance; for Dante says explicitly in the same chapter of the Convivio that Mars is hot like fire, that this is the cause of his colour,[686] and that he dries up and burns things.[687]
Similarly he appears to have believed that Saturn and the moon were literally of a cold nature. “Quel pianeta che conforta il gelo,”[688] in Canzone xv. is doubtless Saturn; and the chill of the hour before dawn is described as due not only to loss of heat by the earth but sometimes also to the influence of the cold moon or of Saturn.[689]
Besides her shadowy markings, the moon had another peculiarity which distinguished her from all other heavenly bodies, for she was the only planet then known to vary in apparent size and shape “according to the way in which the sun looks upon her.”[690] She was therefore a very dark body, though it was believed that she had some light of her own, and Dante argues in favour of this that she does not become totally invisible during an eclipse.[691] This was a very natural conclusion: it would not readily occur to anyone that the reddish light of the eclipsed moon is sunlight refracted (i.e. bent out of its direct course) in passing through the earth’s atmosphere.
The sun, although the astrologers made him not very much larger than the brightest fixed stars and the largest planets, was much brighter and hotter than any, and it was universally agreed that all obtained their light from him. Even if, like the Moon, they had some light of their own, and did not only reflect like mirrors, this inherent light had originally come from the sun and was but absorbed sunlight.[692] We meet constantly with this idea in Dante’s works. In one of his Odes the sun is said to “donar luce alle stelle;”[693] in the Convivio he says, “Il sole ... di sensibile luce sè prima, e poi tutti i corpi celestiali ed elementali allumina.”[694] The Morning Star is described as deriving her beauty from the sun;[695] and after the sun has set he shines forth again in the light of all the stars.[696]
So also says Brunetto Latini, “Sans faille li solaus est fondemenz de toutès lumieres et de toute chalor.”
4. INFLUENCE OF THE SPHERES ON
HUMAN AFFAIRS.
If we are to believe a fifteenth century biographer, we have so far omitted to mention Dante’s greatest claim to be considered a proficient in astronomy. “He foretold,” says Filelfo, “many of the calamities of Florence, the wars of Italy, and other political changes, all of which would have been impossible without an accurate knowledge of the movements of the celestial bodies.”
Filelfo was a poet, and his authority for this surprising statement can be no other than that on which, Dr. Moore says, he mainly depends, and which seldom or never fails him, “his own most airy and lively imagination unembarrassed by any references to documents.”[697] The prophecies of the Divina Commedia are obviously written after the events, and in no single instance are they supposed to have any connection with the art of the astrologers. On the contrary, it is remarkable how very little we find in Dante’s writings about the fate-predicting and character-reading which passed as the chief part of astronomy with the large majority of his contemporaries, and played a considerable part even in the scientific writings of his fellow authors.
Not that he disbelieved in the art: it would have been almost a miracle if he had. The astrologers in the fourth Bolgia were punished with other soothsayers not because they deceived credulous clients, but because they had desired to look too deeply into the future,[698] which was impiety. For this reason the learned Michael Scot, the honoured of Popes, was there, as well as poor Asdente, and Guido Bonatti, and Aruns who from his solitary cave had watched the stars, and prophesied the victories of Cæsar over Pompey.[699] This orthodox sentiment that “judicial astronomy,” was apt to be a snare, and lead to practices condemned by the Church, may have been one reason for Dante’s avoidance of it; but we cannot read his works without feeling that it was the beauty of the skies, and the keen desire to understand the structure of the universe which inspired him to study astronomy, and that he had no superstitious fear of the heavenly bodies, no greedy wish to make use of his knowledge to pry into the future. There is no evidence that he was acquainted with the details of astrology. The few allusions made in his works to special effects of certain stars or planets are only to those most familiarly known, and parallel instances might be found to many of them in modern poems. With this difference, however, that to-day they are figures of speech: with Dante they represented facts. Venus was to him in serious truth “la stella d’amor,”[700] “lo bel pianeta che ad amar conforta,”[701] and exercised a real power over Folco[702] and Cunizza,[703] and his own heart.[704] He even tells us, in serious prose, that it is the planet and not the whole sphere, which is the source of this influence, and that it is borne to us upon her rays.[705] So also the moon has a special influence, which is communicated by her rays.[706]