It is too much to expect readers to work through the voluminous interpretations which have been offered of the very difficult and perplexing mysticism of these cantos. Some points are perhaps plainer to the student who considers them with a fair knowledge of the Bible and history, than to the commentator who wishes to establish a new and original theory. But they are so important (particularly Cantos xxx. and xxxi.) to any one who wishes to understand Dante’s whole position as man, poet, scholar, and politician, that they should not be passed over as mere futile mediæval fancies. It should be said, too, that they contain some passages which will never be out of date until the poetic taste of mankind has altogether changed. § 3. PARADISE. The first point which will strike the reader on entering upon the third division of the poem is the sudden change in the conditions under which the action is carried on. Hitherto Dante has been moving on solid earth, subject to the usual limitations which are enforced by physical laws upon all human action. Henceforth, as he tells us (_Par._, xxx. 123), God operates directly, and physical laws have no longer any place. “It is Beatrice,” he elsewhere says, “who leads on so swiftly from one stage of blessedness to a higher;” and we shall notice that the transference from sphere to sphere is effected by Dante’s fixing his eyes on hers, while she gazes upwards. A word as to the various spheres may not be out of place here. According to the Ptolemaic system of astronomy, as adapted to the requirements of mediæval belief, the earth was at the centre, and concentric with it were ten hollow spheres. In the first eight of these were placed consecutively the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the fixed stars. In order to explain the irregular movements of the planets, “epicycles” or smaller spheres borne by the principal spheres, and bearing the planets, were devised, but these need not be considered here. Outside of the fixed stars came the _primum mobile_, which gave the diurnal revolution of the heavens, and beyond this the Empyrean, or fixed heaven, in which was the special abode of God, and in which all the blessed had their places. Between the earth and the innermost sphere, that of the Moon, lie the regions of water, air, and fire. The Mountain of Purgatory, on the summit of which Dante at the conclusion of the second _Cantica_ was standing, lifts its head as far as the third of these. Through this accordingly, Beatrice and Dante have to rise in order to reach the first step in the celestial ascent. It must be noted that there is no reason to suppose that in every case the actual planet is visited. The “heaven” of the planet embraces the whole “sphere” in which it is set, and its characteristics may be conceived as extending to the whole of that sphere.