The struggle to live is one conflict that creates the vitality for life.  Certainly, the novel ends if the father and son succumb to the conflicts they face in the post- apocalyptic world.  If they surrender, they will most likely die.  Thus, their life and love for one another only survives by facing down the various conflicts and challenges they encounter on their journey to the South.  The idea that McCarthy seems to bring out is that within the struggle for life is life.  Within the perseverance and determination to live is the essence of life, itself. The father is convinced that he must live for his son.  The son understands that he must live for his father.  In this, both characters live life and define life by what they love.  What we end up valuing in life ends up giving meaning to it.  The conflicts they face end up becoming a fundamental test of this passion for life and this need to live.  It is here where the conflicts the characters face help to create life, in terms of why life is worth fighting for.  This becomes a critical element to driving the characters in a setting where despair is evident and pain and suffering are unavoidable.  It is the love for life in terms of what makes life worth living that becomes the most important element in this struggle for existence.