McCarthy has said in an interview that his four year old son john practically co-write the book "i suppose it is a love story to my son" why do you think he said this?

At it's core, The Road is a love story between a man and his son. They struggle to survive together in a dying world. The man would be content to die but his son's life supercede his own. The man is unsure if he is merely prolonging his son's misery but each moment together is reason enough to keep going.