But again, unless it is that sexual complementarity is largely a matter of fitting the genitals together, the unitive purpose is not affected. More importantly, why is it that the genitalia are the only organs exempted from the multipurpose function to which you refer? Why is it so grievous to isolate the unitive purpose in a few acts, when it is no ethical matter at all to isolate any one purpose of any other part of the body for a multitude of acts?
The unitive purpose is not affected?
As far as sexual
union is concerned, sexual complementarity is precisely a function of anatomy. It is precisely the genital difference that makes the unitive purpose possible. Unitive means joining together. The genital differences between male and female are what make sexual union possible.
Human beings are composites of body and soul, but we are not dualistic. The two cannot be separated. One cannot separate the body from the soul, at least not without dying. When we try to separate the emotional and spiritual component of sexual activity from the bodily component, we become de facto dualists. Appealing to the psychological as against the physical splits the human being in two.
Whether or not a psychological tendency to homosexuality or to any other sexual tendency is genetic is a matter of dispute. There is no doubt, however, that anatomy is innate and genetic. Two persons of the same sex are not capable of sexual union. They may be capable of love, friendship, brotherhood, sisterhood, and social activities. They are not capable of sexual union. One might have a hard time proving that “orientation” is genetic; there is no doubt that anatomy is genetic. What does that have to do with sexual complementarity? I would say that it’s basic.
As to multipurpose organs, probably most of our bodily organs are not multipurpose. Liver, pancreas, gut, heart, arteries, veins, capillaries, the CNS and brain, sense organs, and well, yes, ovaries and testes, these all have pretty specific functions.