Some people (and fictional characters) admit to lack of sexual interest.
Andrei Platonov's fictional character Zakhar Pavlovich said, and the character Alexander reacted:
"every man has an entire imperialism down there, in the lower place...."
Alexander could not feel the imperialism within his own body, even though he deliberately imagined himself naked.
The mathematician Paul Erdos said:
Actually, I have an abnormality. I can't stand sexual pleasure. It's a curious abnormality. It's almost unique.
Nina FitzPatrick wrote a fictional character of a priest who initially does not feel sexual but then finds himself attracted to a woman:
Father Francis had never got an erection while listening to a beautiful woman. Or a man for that matter. It dawned on him, not for the first time, that he was born to indifference the way cuckoos are born to neglect their young.
* * *
It was odd to hear her addressing him as Francis rather than Father Francis. He felt it defrocked and re-penised him.
Alternatively, some people begin life with a strong sexual interest that wanes over time for various reasons. Evans D. Hopkins wrote:
Have I become a prude, in prison, you may ask? I don't think so. Rather, I have chosen celibacy as an exercise, as a means of withdrawing from the immediacy of the visceral world, in order to see things with greater clarity. Standing at some remove is almost a prerequisite for sanity in prison; the immediate world is one of clanking bars, piercing announcements, echoing shouts. The discipline of celibacy is a means of escape, of transcendence, of maintaining self-control. So no, I am hardly a prude. Sometimes I want a woman so bad I ache – longing not just for sex but for the feminine voice, the gentle touch or just the image of someone who cares for me to hang on my wall. But I have come to understand that human sexuality is a precious and powerful force that affects us both in its presence and its absence. ... The desire for sex, I have concluded, is often a guise of the broader need for human joy, and sex doesn't always satisfy that need. At the risk of sounding square, I think I have learned to satisfy my deepest needs through writing; I feel I've been able to call upon that emotional quality referred to by early philosophers as agape – love of truth, justice, beauty and humanity. I believe that my period of celibacy has helped me ground myself for this greater purpose. I no longer feel in danger of losing moral focus, or relying upon a relationship to define myself. I am by myself beneath these trees and great sky, but I am not alone. I turn to a fresh page from my notebook, and begin to draft an ad for the personals: Single Black Male, seeking special lady who wants something real this time...
Andrei Platonov. Chevengur. Translated by Anthony Olcott. Ann Arbor: Ardis, 1978 (written 1928). p 48.
Paul Erdos, interviewed in a 1993 documentary
Nina FitzPatrick. Daimons. Boston: Justin, Charles & Co, 2003. pp. 48-49, 143.
"Sex and the (Somewhat) Celibate Prisoner." Evans D. Hopkins. ©1997 Evans Hopkins and Nerve.com