“Thou shalt learn the burning nature of the pure clear sun, thou shalt hear the wandering nature of the round-eyed moon, and thou shalt learn of the surrounding heaven, whence it arose, and how Necessity guiding it compelled it to hold fast the bounds of the stars.” _Parmenides._ 1. THE SPHERES. Dante’s astronomical phenomena, though they are just the same that are familiar (or ought to be familiar) to us, have led us into some strange by-ways, because they are so intimately connected with his works of imagination. His astronomical theories, by which these phenomena were explained, will also take us into paths which are now seldom trodden by astronomers or others, because mediæval astronomy was mingled with magic, with metaphysics, and with religion, in a way which seems very strange to us. The second treatise of the _Convivio_ has for its text the Ode which is quoted in _Paradiso_ viii. 37, “Voi che intendendo il terzo ciel movete.”[565] When speaking of the literal meaning of this Ode, Dante takes the occasion to discourse on the system of astronomy which he had learned, and describes how all the apparent movements of the heavens are explained by postulating the existence of spheres and epicycles, entering with special detail into the system of Venus, the third heaven; and later on, when expounding the allegorical meaning of the Ode, he draws an elaborate comparison between the spheres and the different branches of science and philosophy, in which he incidentally gives his readers a good deal of information about the heavens. ------------------------------------------------------------------------ [565] “Oh ye whose intellectual ministry Moves the third heaven.” (_Carey_). ------------------------------------------------------------------------ From this interesting treatise, therefore, as well as from many scattered passages in all his works, we learn what Dante thought were the real movements of the heavenly bodies, their dimensions, their nature, and the forces which move them; and it forms a valuable commentary on the _Paradiso_, in reading which he supposes us to understand the elements of the Ptolemaic system, and the ideas of the philosophers and the Fathers of the Church concerning the organization of the Universe. Of these ultimate truths concerning the heavens, Dante says, very little can be known, but the little which is within the reach of human reason, gives more delight (as Aristotle says) than the abundance and the certainty of other things easier to be understood.[566] This thought finds an echo in the _Paradiso_, where the poet reminds us of the beautiful order to be found throughout the universe, and invites us to contemplate the skill of the architect as shown in the movements of the planets.[567] ------------------------------------------------------------------------ [566] _Conv._ II. iii. 8-14.