Our speaker is a smart guy. He seems like someone you'd trust and someone who has an inquisitive mind. Great dinner date, this guy, right? Okay, maybe not that, but he's definitely got big things on his mind, like God and the paradoxical nature of God's creation. That's not exactly idle chit-chat.
Okay, so he's a little intense, but he's also interesting to talk to. He's probably Christian because he's talking about God from the viewpoint of Christian tradition. He's wondering why, if God's so good, such terrible things exist in the world. He gives God the benefit of the doubt, and says that he's sure God could explain, but God doesn't bother explaining Himself to humans who are too busy with "petty cares." It's like he's saying, "Look, I know God's good, but what's up with all the bad stuff in life?"
He also likes to name drop Greek myths. Referencing Tantalus and Sisyphus works perfect because they're examples from life that seem to contradict God's goodness; however, they also mark the speaker's intellectual abilities. Our speaker knows his stuff and he's laying it down heavy while he tries to work out the unknowable nature of God. He wants us to know that he's educated and no doubt about it, we're listening to a well-informed speaker.
All this seems to lead up to his final statement at the end of poem. He's set up his audience in a way. He begins by sounding reasonable. Sure, God's good, and could explain the mysterious nature of suffering if He wanted to. But God is beyond all that, he says, and can't be bothered by our petty confusions.
Ah, but it's that strange paradox of knowing and not knowing that inspires the speaker. Even though he can't know, he still wonders how God could make black poets and inspire them to sing. During a time when black artists were just starting to be recognized and taken seriously in America, this transition was a great topic for the speaker.
So not only is he mister smarty pants laying down perfectly metered, rhymed sonnets that inquire about the nature of God's mind (whew!), but he's also concerned with race relations in America. Being black and a poet may have seemed like somewhat of a contradiction to white America at the time, and our speaker finds that crucial to his understanding of who he is and why he exists. Our speaker admits he can't know why God does what He does, but his desire to ask and wonder about God is what inspires him to sing, a.k.a. write awesome sonnets.