French philosopher Michel Foucault was himself gay but claimed that sexual orientation is a social construct, rather than anything "natural". This has been misinterpreted as implying that homosexuality is a choice. The battle between "essentialists" and "constructivists" has raged ever since.
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Foucault asserted that homosexuality is not born of nature or nurture, but is socially constructed. When doctors created the profusion of perversions, they unwittingly produced the models that gave rise to gay, lesbian, and other sexualities. In Foucault's opinion, these identities are themselves a form of oppression...
http://www.planetout.com/pno/news/history/archive/foucault.htmlSince Foucault regarded sexual orientation as an artifice, he dismissed gay liberation. Asked about gay marriage, he'd probably call it
irrelevant and counterproductive.