One of the problems with the theory of gender complementarity is that it tends to reduce the human to the visually physical. Heterosexuality is held to be normative on the basis of gross anatomy — the fact that male and female bodies exist is taken uncritically to mean that they not only can join, but only can join. This biological determinism ignores that much (if not most) of sexuality is mental and emotional — and that these aspects of the human being are also just as much physical (in the brain and nervous system, in particular as acted upon by the endocrine system) as the gross anatomy of the external sexual characteristics. The “dishonorable members” cannot say to the brain, “I have no need of you.” Every member shares in the wholeness of the body.
The essence of sexuality, as in so much else about what it means to be human, lies in the inside, not the outside: it is content, not form alone, that constitutes the human person.
Tobias Stanislas Haller BSG