Frederic walks away alone in the rain, chastened by his experiences and feeling alone in the universe.
Hemingway suggests that the only true values people can cling to are in individual human relationships, not in abstract ideas of patriotism or service
His own wound, however, teaches him to value life and prepares him to enter into a love relationship with Catherine.
By the end of the novel, with love and hope seemingly dead, he has come to an understanding that one must be engaged in life, despite the vicissitudes of an indifferent universe.