I presume that you are talking about Raymond Carver's classic short story "Cathedral." The short story features many of the stylistic aspects that are defining qualities for Carver's pioneering style of minimalist prose. Chief among these is Carver's refusal to provide the names of either the narrator or his wife. Carver's aversion to illustrating such details pushes readers to engage with the structure, sparse dialogue, and striking imagery in a deeper manner.
Therefore, it is initially surprising that Carver intentionally gives readers Robert's name. When we look at the protagonist's limited perspective, however, Carver's decision becomes more obvious. Carver is pointing out that Robert, despite the disability that the protagonist initially judges him for, is the most self-aware of the characters in the story. He has the most solid sense of himself, whereas the protagonist is lost. It takes Robert's intervention to provide an epiphany to the protagonist, and give him a small moment that has a profound impact on the way he perceives life.