"For the sake of goodness and love, man shall let death have no sovereignty over his thoughts." - Thomas Mann
To Govern. Supreme power or authority.
Often times religion is a cultural system relating mostly to humanity, that establishes thoughts,ideas and morals that contribute to an individuals values. Often times those "values" become a "merit" or "worth" in a society and suddenly those who do not share the same "values" lack "merit". When a cultural system (ahem, religion) becomes such a cycle it often governs (rather than influencing) many lives and choices. I believe Thomas Mann is advising us to let "goodness and love" govern our thoughts.