"The love of God, unutterable and perfect, flows into a pure soul the way light rushes into a transparent object. The more love that it finds, the more it gives itself: so that, as we grow clear and open, the more complete the joy of heaven is. And the more souls who resonate together, the greater the intensity of their love, and, mirror like, each soul reflects the other.
And here Dante describes an evidently spherical world... "The lamp of the world [the sun] rises to mortals through different passages; but through that which joins four circles with three crosses [the position of the rising sun at the vernal equinox] it issues with a better course and conjoined with better stars, and tempers and stamps the wax of the world more after its own fashion. Although such an outlet had made morning there and evening here, and all the hemisphere there was bright, and the other dark..."
And when he had put his hand on mine with a cheerful look, wherefrom I took courage, he brought me within to the secret things. Here sighs, laments, and deep wailings were resounding through the starless air; wherefore at first I wept thereat. Strange tongues, horrible utterances, words of woe, accents of anger, voices high and faint, and sounds of hands with them, were making a tumult which whirls always in that air forever dark, like the sand when the whirlwind breathes.
The purpose of the whole [the Comedy] and of this portion [the Paradiso] is to remove those who are living in this life from the state of wretchedness, and to lead them to the state of blessedness.