The Road by Cormac McCarthy shows that the boy could not survive without his father, but why did the father need the boy?

In the dehumanized, post-apocalyptic world of this novel, the father needs the boy, his son, for psychological reasons. Caring for and protecting the boy gives the father's life meaning and purpose, a reason to keep on living in a bleak, barren world filled with hunger, fear, violence, cannibalism, and hopelessness. Second, looking out for someone beyond himself, especially someone weaker and more vulnerable, helps keep the father human. The boy is someone the father can love, and with the boy, the father can create a community, tiny as that community of just two human beings is. While their bond may seem insignificant, it's vital, for this world has turned into one in which people are isolated, fighting and preying on each other for scanty bits of food. It is dangerous for the father to trust any other person than his son. Further, the father is dying, and having the son to protect gives him the motivation to stay alive for as long as possible.