The Galaxy or Milky Way is twice referred to in the Divine Comedy. In Inf. xvii. 106-108, it is in connection with the myth of Phaeton, who being allowed by his father Jove to drive the chariot of the sun for one day, lost control of his chargers, and going all astray, burned the sky in a part which still shows signs of this catastrophe, i.e. the Milky Way.

This of course is only a poetical myth. But in the Paradiso, in three lines the appearance, colour, and approximate position of the Galaxy are described, and allusion is made to the difference of opinions between learned men with regard to the puzzling question of its nature. Dante is in the heaven of Mars. He sees the soldier saints, star-like and fiery red, some larger and some less, thronging thick in two great bands, which, crossing one another in the depths of the planet, form a marvellous Crucifix. The crowded lights make him think of the Galaxy, with its multitudinous points of light, differing in brightness, although that is white, and lies in a great circle between the celestial poles.

If we now turn to the fifteenth chapter of Treatise II. of the Convivio, we shall find the Phaeton myth and the various theories about the Milky Way set forth in due order, and shall learn which of these Dante considered to be true.

He is comparing the two sciences of Metaphysics and Physics with the Heaven of the Fixed Stars, and takes the opportunity to tell us some of the most important facts known about it. Here he calls the Galaxy a circle:—“La Galassia, cioè quello bianco cerchio che il vulgo chiama la Via de Santo Jacopo.”[321] This popular name perhaps arose through a confusion of Galaxy and Galicia, where was a famous shrine of St. James, and hence came the belief in Italy that the Galassia was a sign by night to guide pilgrims on their way to this shrine at Compostella in Galizia.

Dante proceeds as follows with his comparison:—

“E per la Galassia, ha questo cielo grande similitudine colla Metafisica. Perchè è da sapere che di quella Galassia li filosofi hanno avuto diverse opinioni. Chè li Pittagorici dissero che ’l sole alcuna fiata errò nella sua via, e, passando per altre parti non convenienti al suo fervore, arse il luogo, per lo quale passò; e rimasevi quell’ apparenza dell’ arsura. E credo che si mossero dalla favola di Fetonte, la quale narra Ovidio nel principio del secondo di Metamorfoseos. Altri dissero (siccome fu Anassagora e Democrito) che ciò era lume del sole ripercosso in quella parte. E queste opinioni con ragioni dimostrative riprovarono. Quello che Aristotile si dicesse di ciò, non si può bene sapere, perchè la sua sentenza non si trova cotale nell’ una traslazione come nell’ altra. E credo che fosse l’errore de’ traslatori; che nella Nuova par dicere che ciò sia uno raunamento di vapori sotto le stelle di quelle parte, che sempre traggono quelli; e questa non pare avere ragione vera. Nella Vecchia dice, che la Galassia non è altro che multitudine di stelle fisse in quella parte, tanto picciole che distinguere di quaggiù non le potemo, ma di loro apparisce quello albore il quale noi chiamiamo Galassia. [E puote essere che il cielo in quella parte è più spesso, e però ritiene e ripresenta quello lume] e questa opinione pare avere, con Aristotile, Avicenna e Tolommeo. Onde conciossiacosachè la Galassia sia uno effetto di quelle stelle le quali non potemo vedere, se non per lo effetto loro intendiamo quelle cose, e la Metafisica tratta delle prime sustanze, le quali noi non potemo simigliantemente intendere se non per li loro effetti; manifesto è che ’l cielo stellato ha grande similitudine colla Metafisica.”[322]

This characteristic passage is interesting for several reasons. It illustrates the mediæval fondness for allegory, the reluctance to believe that Aristotle could ever be wrong, and the interest in ancient Greek speculations, in all of which Dante expresses the feelings of his age: and it brings vividly before us the methods and the difficulties of mediæval authors. For Dante is repeating from Albertus Magnus all these ancient speculations: the officious copyist who altered Aristotle’s words, the fact that Aristotle could only be read in Latin, and the variety of translations, were all everyday obstacles to study; and Dante’s own book has suffered from one of them in this very passage. The words placed between brackets are evidently an interpolation (as Mr. Wicksteed observes in the “Temple” Convivio): without them the passage goes on smoothly and logically to its end. On the assumption that the Galaxy is composed of a multitude of small stars, but not that the sky is denser in that part, the parallel with Metaphysics holds good.

Dante therefore held the true opinion about the Milky Way, but he was mistaken in thinking that he had the support of Aristotle. It was the “New Translation” (made by Aquinas from the Greek) which gave his opinion correctly; in the “Old” (made by Michael Scot from the Arabic) his statement had been apparently changed without comment into one which seems to Dante—and also to us—to represent the truth about the Galaxy.