In The Road by Cormac McCarthy, the man and the boy have been reduced to their basic existential states.
Since there are no longer friends and family and no real society, the identification of the man and the boy is only important to them as they are on the most basic level of living. For this same reason, in certain editions of the novel there are no designated chapters as the search for food and shelter is a continuum without a new beginning or a new phase.
It is only the sustaining net of love that holds these two beings together. Otherwise, they are isolated in a post-apocalyptic environment that is reduced to a struggle to survive:
They plodded on, thin and filthy as street addicts. Cowled in their blankets against the cold and their breath smoking, shuffling through the black and silky drifts. . . . He held the boy against him, cold to the bone. Don't lose heart, he said. We'll be all right (p.177).
The man represents all that remains of goodness in a demolished civilization. He desperately clings to life as he hopes that his son will survive and not be corrupted as have so many others. When the man dies, he goes with the hope that "goodness will find the little boy."