David has a lot of ideas about what it means to be a man. He articulates some of them, and he leaves others implicit. His relationship with his father early on in the book begins to shape his ideas in ways that he does not even realize. One of David's problems in Giovanni's Room is that his idea of manhood is not flexible enough to adapt to his changing circumstances, specifically his romantic relationship with Giovanni.
David hopes to marry Hella because he believes that would confirm his masculinity; to David, being a man involves loving and desiring women.