In Canto II Beatrice and Dante are taken to the celestial sphere of the moon by a dense luminous cloud. Dante does not understand how his body can interpenetrates the moon, that is, how two dimension can be in one. This is not surprising, he says, since we do not understand how God dwelt in the humanity of Christ.
Dante sees a group of vague faces eager to speak with him and thinks they are reflections. So, he looks back but sees nothing. Beatrice tells him, "True substances are these [real souls] thou dost perceive, who broke their vows, and so are cloistered here." (Canto 3.28)
Plato had "taught" that at death the soul returns to their star, yet he may not have desired to take his teaching literally. Beatrice explains:
"They are shown thee here, not that they here reside,
Allotted to this sphere; their heavenly mansion,
Being least exulted is thus signified." (Canto 4:37)
Dante meets Piccarda who tells him that she had joined a convent of the Poor Clares and taken vows but was forced by her brother to leave the convent and marry. But in her heart she had never taken off her veil or the desire to dedicate her life to God. Because she had broken her vow, she was now in the lower heaven. In Canto IV Beatrice sees a doubt in Dante's mind: How can it be right for her to lose merit in God's eyes? After all she was forced to leave the convent!
Beatrice explains to Dante that those with absolute will do not sin such as St. Lawrence who was fried on a grill rather than deny his faith. Yet Piccarda and others have sinned to the extent that they did not refuse out of fear that something worse may happen. Piccarda's absolute will was qualified when she consented.
Dante asks Piccarda if she has a desire to go higher, to gain more insight into God's knowledge and love. She answers:
"Brother, our love has laid our will to rest,
Making us long only for what is ours,
and by no other thirst to be possessed.
...His will is our peace. (Canto 3.70, 85)
Dante also meets Constance the Great, mother of Frederick II who, it was believed, also was taken from the Convent to marry Henry VI. She spoke and while vanishing began to sing --
(from recording Sacred Polyphony: Ave Maria)
Ave Maria, gratia plena,
Dominus tecum;benedicta tu mulieribus,
et benedictus fructus ventris tui Iesus.
Sancta Maria, regina caeli, dulcis et pia,
o mater Dei, ....
5_Mercury: Celestial Rulers