Paradiso Paradise Canto XIV: (Fourth Heaven: Sphere of the Sun, Fifth Heaven: Sphere of Mars) Summary
As St. Thomas falls silent, Beatrice begins talking.
She says that Dante needs "to reach the root of still another truth." She requests that the spirits tell Dante whether or not the light the souls emit will stay forever. If so, then how – when they receive their bodies back – will be able to look on such bright light and not be harmed?
The ring of spirits, listening intently to Beatrice's request, gives a shout of joy, and begins singing about the Trinity.
As the spirits wheel around, a modest voice (from King Solomon) floats up from the inner circle and says, so long as we all stay in Heaven, our clothing will be these brilliant lights. The degree of our brightness depends on how much we love God, and that is measured by how well we see. Our vision is in turn measured by how much grace (or unmerited love) we receive from God. On Judgment Day, we'll all be reunited with our bodies. Then we shall be complete. Whatever extra light we have left will be enhanced because God will love us more, for our perfection.
In answer to the second part of the question, Solomon answers that when our bodies are united with our souls, the body's organs will become stronger (as a result of being complete) and we won't be blinded by our light.
Solomon's fellow dancers agree so heartily with this that they nearly trip over their tongues saying "Amen," making Dante see how eager they are to have their bodies back.
But look! Dante's eyes shift towards the horizon and he sees the light growing even brighter there, as if new spirits are approaching.
Beatrice decides she wants to join in on the light show and, to Dante's astonishment, she grows even more beautiful (and brighter). In fact, she's so beautiful that Dante cannot describe her in words.
When he finally tears his eyes away from her, he does a double take and realizes he's standing on red ground, and that they're in the next sphere, the heaven of Mars.
As has become custom, Dante takes this moment to thank God for allowing him to rise so high. As soon as he speaks, he knows his thanks will be accepted. (Dante sees a sign – two bright rays of light, that he takes to be God's acceptance.
Those two rays of light aren't just any rays, they actually form a cross. Yes, the cross.
Dante is astonished, but he does actually describe it a little. He talks about how the souls move across from bar to bar like streaks of light glimmering down the metal bars of umbrellas. They are singing in perfect counterpoint a hymn that Dante doesn't recognize.
He notes that his words may seem presumptuous for daring to describe in human terms what man cannot possibly understood.
Just like this cross, Beatrice's eyes grow ever more lovely the higher she ascends.