What is Countee Cullen trying to say about God/religion in "Yet I Do Marvel"? Also, what is the meaning of his Greek mythology references to Tantalus and Sisyphus?
In this poem Cullen reaffirms faith in God by (ironically) focusing on examples of injustice. Cullen considers that if God would "stoop" (come down to the world and/or humanity's mental level) in order to explain why these injustices occur, humanity would not understand because God's ways are "inscrutable" (hard or impossible to understand). The human mind is too concerned with "petty cares" to comprehend God's "awful" (full of awe and wonder) mind.
Despite all of the injustice in the world, the speaker/Cullen marvels that, for example, he should be subject to discrimination (being black) and yet gifted with the desire to sing and write poetry. Thus, the poet sings in spite of his oppression. Tantalus continues to try to reach the fruit despite never actually being able to reach it. Sisyphus continues to push the rock up the hill despite his inevitable failure. Instead of being disheartened by all these examples of seemingly useless struggle, the speaker of the poem concludes that since God's ways are mysterious and inscrutable, there must be some reason that people continue to struggle in the face of seemingly impossible obstacles. The reason must be some universal determination to affirm life, a determination with its roots in an underlying faith in God. The poet sings because it is the right thing to do.