The term “homosexuality” appears by the end of the 19th century, at the very time when religious power is repelled from fields of knowledge and social organization on behalf of medical authority.
From that time forth, treatment replaces blame. To this end, the medical world, always eager to categorize, creates the word “homosexual” (1885) as referring to a mental disease. The term “heterosexual” appears at the same time as well.
Since then, lots of surveys have been compiled aiming at possible cause(s) of homosexuality, and eager to provide suitable treatment. Cause(s) of heterosexuality didn't raise the same interest. All these surveys may be classified into two main lines of thought: