“Il foco movesi in altura, Per la sua forma, ch’ è nata a salire Là dove più in sua materia dura.”[738]
That is to say the form of a flame fits it to rise to that place where, being in its own element, it may last longer than on Earth. Conversely, the centre of the earth is described as the bottom of the whole universe, and the point towards which all weights are attracted.[739] These opposite forces Dante calls gravity and levity.[740]
The most interesting illustration of this force of gravity is the description, in the last canto of the Inferno, of passing the centre of the earth, “il punto al qual si traggon d’ogni parte i pesi.”[741] Virgil turned here “con fatica e con angoscia,”[742] and bid Dante hold him fast, “ansando com’ uom lasso.”[743] It was natural to suppose that the force of gravity would increase as one neared the centre, though the fact is that it decreases. In deep mines it is less than at the surface of earth; and if we could go to much greater depths we should find that we could stand in any position, and walk in any direction with almost equal ease, till at the exact centre the sense of weight and of “up” and “down” would vanish altogether. This is because it is the whole mass of the earth which attracts, and when we penetrate beneath the surface the part above is no longer dragging us down, and its effect is annulled. But at the surface gravity acts as if the force were all concentrated at the centre, and falling bodies increase their speed as they approach the surface: before the days of Newton, therefore, it was thought that the whole of the attracting force was actually situated at the centre of the earth. Brunetto Latini speaks of gravity increasing as this point is approached, and Dante, like Aristotle, calls it the goal of gravity.[744]
Between the physical and the spiritual universe as conceived by Dante, there is a very close correspondence. Souls burdened with the weight of sin fall towards the centre of the universe, sinking deeper the heavier is their guilt, and at the bottom of the whole universe is the personification of all evil. Repentant souls, as they are freed from their sins, rise higher and higher, and the ascent becomes always easier, until at last they soar heavenward as naturally and spontaneously as flames of fire. In Paradise the motion of the pure spirits is inconceivably rapid, and their mystic dances expressive of joy are always in circles.
Motion in circles was the only appropriate kind for the heavenly bodies,[745] but the actual force which originated and preserved their motions was intelligence and will. When Dante sang, “Voi che intendendo il terzo ciel movete,”[746] he was not addressing beings created merely by his poet’s imagination. His own commentary on the words shows us that they were as real to him as the planets themselves. He can know nothing of them through the senses, yet is as certain of their existence as one with closed eyes is of light.[747] These beings move the spheres not through any material contact, but solely by the power of thought: they are immaterial immortal intelligences, commonly called Angels, and Dante identifies them with the Forms of Aristotle, the Ideas of Plato, and the gods and goddesses of the Pagans, “avvegnachè non così filosoficamente intendessero quelle come Plato.”[748] As the hammer beats out forms in metal, and thus expresses what is in the mind of the smith, and as he works from the artist’s design, so the movements and “virtues” of the sacred spheres mould earthly events, but these movements and virtues are the expression of controlling angels, and they are carrying out the Will of the First Mover. And as the joy of a happy mortal shines out in the eyes, so the joy of the angels shines out in stars and planets.[749]
There were nine Orders in the angelic hierarchies, according to the teaching of the Church, the chief authority on this subject being a book De Celestia Hierarchia, supposed to have been written by Dionysius the Areopagite, a disciple of St. Paul, who had learned from the apostle what he had seen when rapt to the third heaven. Aquinas assigns to one of these nine orders the guidance of stars and planets, and to others the rule over earthly affairs. But since the latter follow the celestial motions, there was no need to separate the two functions, and Dante laid down in the Convivio that a few Angels from each Order preside over the movements of each sphere. With Aristotle, he agreed that there is one Intelligence for each movement, so that for Venus (for instance) there are three movers to direct respectively the circling of the Epicycle, the Deferent, and the movement of Precession which every planet shares with the stars; but whether there is a fourth mover to guide the diurnal motion of Venus or if all the inner spheres are swept along by the motion of the Primum Mobile, he would not presume to decide.[750]
When he wrote the Paradiso, he no longer thought that a few Angels were set apart for this ministry: he implies that all the angels in each order united in the act of moving a whole heaven and perhaps he means to include the beatified human spirits as well.[751] He also slightly changes the correspondence between the angelic orders and their respective spheres.[752]
Swiftness of motion in a sphere corresponds with fervour of adoration in the Movers: hence the highest and swiftest of the moving heavens, which is the Primum Mobile, is moved by the highest Order, the Seraphim: and the lowest and slowest, which is that of the moon, by the lowest order, the Angels.[753]
All these movements are a proof of the existence of a First Mover, Himself unmoved, as Aquinas had said, following Aristotle, and the first words of Dante’s confession of faith in Paradise are an echo of this:—
“Io credo in uno Iddio, Solo ed eterno, che tutto il ciel muove, Non moto, con amore e con disio.”[754]