Besides these, there is evidence in his writings that he was familiar with several classical authors who treated of astronomy. He quotes frequently from many of Cicero’s works, and we find echoes, in two passages, of the Dream of Scipio,[104] which he is almost certain to have read, since it was a favourite book in his time. There are several references to Seneca, but the only time that an astronomical phenomenon recorded by him is mentioned[105] Dante is evidently quoting at second-hand from Albertus Magnus. With all the works of Virgil, and with the Metamorphoses of Ovid (from which he took his astronomical myths)[106] he was evidently very familiar; and Lucan is one of his authorities for the position of the earth’s equator. In this case the name of the author and the number of the book are precisely stated.[107]
Dante had a great reverence for Plato, whom he calls “uomo eccellentissimo,”[108] and of whom he repeats the mediæval legend that he was a prince who gave up all for the sake of acquiring wisdom.[109] Of his writings he only knew the Timaeus, probably the Latin translation and commentary of Chalcidius, which was widely known. Or he may have been acquainted with Aquinas’ commentary, which has since been lost. He also knew something of Plato’s teachings through Aristotle and Cicero, Albertus Magnus, and Aquinas, and perhaps St. Augustine. When he feels obliged to dissent from the great philosopher’s doctrine that the souls of men come from the stars, he does so with reluctance and great gentleness.[110]
Among other Greek philosophers who speculated on astronomy, Dante mentions Thales[111] and Pythagoras. The date when the latter flourished he takes (he tells us) from Livy, and his theory that the Universe is governed by the principle of number from Aristotle’s first book of Metaphysics. The astronomical theories of his school are also doubtless taken from Aristotle. Dante tells the story of Pythagoras that he was the first man to be called “philosopher,” because when asked if he considered himself a wise man, he replied, “No, but only a lover of wisdom.”[112] Dionysius the Academician and Socrates are referred to for their opinions on the influence of the stars upon human souls;[113] and Anaxagoras and Democritus for their galactic theories,[114] which Dante obtained from Albertus Magnus.
Except for Alfraganus, Dante refers but seldom to Arab astronomers. He does not seem to have known Albategnius. The De Substantia Orbis of Averroës is quoted in the Quæstio de Aqua et Terra,[115] and it is possible that from this book Dante derived a theory about the moon which he expounds in the Convivio. He quotes Alpetragius on circular existence (dependent on the spheres),[116] Avicenna on the Galaxy, and again with Algazel on the influence of the spheres,[117] and Albumassar on meteors.[118] The quotation from the latter, however, is second-hand from Albertus Magnus, and is a mistake, for the passage is not to be found in that astronomer’s works. He was born in Turkestan, in 805.
We may here remind our readers that the three Latin poets, Virgil, Ovid, and Lucan, were among the world’s five greatest poets met by Dante in Limbo; that next to Aristotle among the philosophers stood Socrates and Plato, and near these were Democritus, Anaxagoras, and Thales, Cicero and Seneca, Ptolemy, Avicenna and Averroës.[119]
Among Christian writers, Dante may have gathered some information about ancient Greek speculations from St. Augustine and Peter Lombard; and Orosius, the Spanish friend of Augustine, was his chief authority for that geographical system which, in connection with astronomy, plays an important part in the time-indications of the Divina Commedia. Orosius had a great reputation among geographers and map-makers. He had travelled much between Spain, Africa, and Palestine, and he devotes a chapter to describing the different parts of the earth in his history Adversus Paganos, which he wrote to prove that Christianity had not injured but benefitted the countries in which it had been accepted. This fifth century geography seems to have been largely based on the first-century geography of Strabo, who quotes Eratosthenes, Posidonius, and Hipparchus among his authorities. Orosius states that the land is entirely surrounded by Ocean, and is divided into three continents—Asia, with the mouths of Ganges in the middle of its eastern coast, Europe stretching vaguely very far to the north-east, and Africa a narrow and long strip from east to west between the Mediterranean and the southern ocean. This chapter is quoted in De Mon. II. iii. 87-90 and Qu. xix. 43; and Orosius is almost certainly “quell’ avocato dei tempi cristiani,”[120] seen by Dante among the learned doctors in the Heaven of the Sun.
The speaker who points him out in these words also mentions his own name and that of the spirit nearest to him:—
“Questi che m’è a destro più vicino Frate e maestro fummi, ed esso Alberto È di Cologna, ed io Thomas d’Aquino.”[121]
These two, so near in heaven, had been close companions on earth. The youthful Thomas, son of Count d’Aquino in southern Italy, after six years’ study at the University of Naples joined the Dominican Order, and went to Cologne to learn from Albert, who was also of noble family but born in Suabia on the Danube. Together they went to Paris, together returned to Cologne, but after six more years there their paths separated: Albert rose to be Bishop of Ratisbon; Aquinas, after lecturing in Paris, Rome, and Bologna, became a professor at Naples, and died in Italy in 1274. His master survived him by six years, dying at Cologne at the advanced age of eighty-seven in 1280.[122]
These two are in the foremost rank among authors of his own time who influenced Dante. He quotes both writers and several of their books by name,[123] and though he never mentions it he was very familiar with the Summa Theologica of Aquinas. To the works of these famous authors he was frequently indebted for astronomical facts, theories, and history, as already noted. Besides this, his reverence for Aristotle, his belief in the essential harmony between religion and science, and his whole attitude towards knowledge, are greatly due to the influence of St. Thomas and his “brother and master,” Albert of Cologne.