Immortality does not inhere in a human being but rests on a relation, on a relationship, with what is eternal, what makes eternity meaningful. This abidingness, which gives life and can fulfill it, is truth. It is also love. Man can therefore live forever, because he is able to have a relationship with that which gives the eternal. "The soul" is our term for that in us which offers a foothold for this relation. Soul is nothing other than man's capacity for relatedness with truth, with love eternal. And in this way, we can get right the real order of priorities: the truth and love that we call "God" give man eternity, and because in the spirit and soul of man matter is integrated, matter attains in him to the fulfilled completeness of the resurrection. 

Joseph Ratzinger