The primary theme that is developed in Bret Anthony Johnston's "Boy" is the traditional expectations of masculinity. The piece is a response to Jamaica Kincaid's story "Girl," which uses a similar structure to explore expectations of femininity.
"Boy" is presumably written from a father's point of view. He gives a long series of instructions to his son about what is needed to demonstrate his manliness and avoid being "the coward [he is] so bent on becoming." The father provides instructions about how to fight successfully, how to treat women, how to kill a dying dog, and how to make money. Men are expected, according to this list of instructions, to know how to build things, repair things, and grow things. Despite all the pressure of living up to a diverse array of expectations, men are also expected to "hold everything in until it turns to bone."
The piece speaks to the difficulty of becoming a man by society's traditional standards. There is a sense that the young boy's needs and desires are lost in this litany of instructions; his voice is only heard twice in the barrage of paternal directives, and his questions are met with scorn and insult.
"Boy" establishes the connections between traditional roles of masculinity and physicality, diminishing the possibility for the boy to forge a path which deviates from this established set of expectations.