Paradise is about what a man can see and what he can say of what he saw. The canticle does not ask what each soul deserves. It asks how far sight can bear to climb, and what is left in the verse when sight goes beyond what language can reach.
The ascent begins as an explanation of order: in canto I Beatrice says that all things have order among themselves and that this is what makes the universe resemble God. Then come freedom and the vow, justice and empire, knowledge, faith and exile, and each subject is a question of Dante's answered by Beatrice or by a saint. The themes that run through it are God and the divine, faith, knowledge and wisdom, justice and law, home, exile and return, language and narration, and love. The rule from on high, given in canto XXVIII, is that being blessed is born of seeing, and loving comes after.
At every height the poet confesses that language does not reach: memory does not keep up with the intellect, the poem has to leap, the pen leaps, and in the end seeing is greater than telling. The confession becomes a subject. The last verse shows where everything moves, and it is not a thesis: it is the love that moves the sun and the other stars.