Although many people[who?] believe that queer theory is only about homosexual representations in literature, it also explores categories of gender, as well as sexual orientation. In fact, it could be argued[by whom?] that queer theory's main project is not the interrogation of homosexuality, but the subverting and challenging of heterosexuality as 'natural' and 'unmarked'. Some[who?] argue that queer theory is a by-product of third-wave feminism, while others[who?] claim that it is a result of the valuation of postmodern minoritizing, that is, the idea that the smallest constituent must have a voice and identity equivalent to all others.
Queer theory's main project is exploring the contesting of the categorization of gender and sexuality. Theorists[who?] claim that identities are not fixed – they cannot be categorized and labeled – because identities consist of many varied components and that to categorize by one characteristic is wrong. For example, a woman can be a woman without being labeled a lesbian or feminist, and she may have a different race from the dominant culture. She should, queer theorists argue, be classed as possessing an individual identity and not put in the collective basket of feminists or of colour or the like.
Queer theory is derived largely from post-structuralist theory, and deconstruction in particular. Starting in the 1970s, a range of authors brought deconstructionist critical approaches to bear on issues of sexual identity, and especially on the construction of a normative "straight" ideology. Queer theorists challenged the validity and consistency of heteronormative discourse, and focused to a large degree on non-heteronormative sexualities and sexual practices.
The term "queer theory" was introduced in 1990, with Eve Kosofsky Sedgwick, Judith Butler, Adrienne Rich and Diana Fuss (all largely following the work of Michel Foucault) being among its foundational proponents. Queer theory should not be confused with queer activism, although there is overlap between the two.
"Queer" as used within queer theory is less an identity than an embodied critique of identity. Major aspects of this critique include: discussion of the role of performance in creating and maintaining identity; discussion of the basis of sexuality and gender, either as natural, essential, or socially constructed; discussion of the way that these identities change or resist change; and discussion of their power relations vis-a-vis heteronormativity.