Unquestionably, Tomas Rivera is criticizing the role that religion plays in the lives of the migrant workers. Since religion is an inherent part of the lives of the characters, it is inevitably a part of almost every story. And Rivera seems to think that religion is one of the oppressive factors keeping the migrant workers in the vicious cycle of a troublesome life full of exploitation and suffering. He criticizes the Church on a moral level: the chapter in which the protagonist sees the nun and the priest making love in the sastreria puts emphasis on its hypocrisy. The young man is trying to find out who he is, his place in society, and religion is a huge obstacle to this. Taught that sex is a sin, something dirty and base, he is told to deny himself and one of the core elements of his identity. He criticizes religion at a grassroots level - where priests find it more important to take donations for the parish fund than to address problems in the community, the problems that Rivera is describing for us.
Rivera takes a very existentialist view on life: the protagonist must make his own live, take control of his own destiny, and break away from the vicious migrant cycle which is partly imposed by religion.
The protagonist questions good and evil...he asks: what is good? what is evil? He curses God and calls out for the Devil, and sees that life is arbitrary, that religion doesn't have control of his life. He questions his mother's belief that there is really a God out there who will grant your wishes if you are good and punish you if you are bad. What kind of God is that, he asks?
In the very end, when he climbs out from under the house, he is free from this oppression...he smiles because he realizes that he is free, he is in control, it is his life to live and no one else's...that he hasn't lost anything, and that everything is related....therefore that everything is in his control.