"You were very particular about growing your hair and wearing trousers, and we certainly had to call you Robert." This is how my father remembers the four or so years of my childhood I spent as a boy. It was prompted, my parents think, by a local farmer's son called Robert, who I was drawn to as a child.

I remember a photograph from this period, of me standing next to my older sister. She is wearing a pretty dress, and an alice band; a toothy grin lights up her face. I have on the most gorgeous deep blue velvet trouser suit, a white frill-collared shirt, and a terribly serious expression. One of my proudest moments, I am told, is when on a family outing to the theatre I am mistaken for a "young man".

What was this about? I dismissed it, later, as a rather embarrassing phase, best forgotten or else laughed away, to do with being a tomboy, whatever that meant. Others had imaginary friends, or teddies with personalities. I had Robert. I was Robert.

Then at university I came across a clutch of books, including Judith Butler's Gender Trouble and Eve Kosofsky Sedgwick's Epistemology of the Closet, of the key texts of queer theory. This strand of critical thinking emerged in the late 80s and early 90s, deliberately appropriating the term of abuse usually hurled at gay people ("queer") in order to challenge its offensive meaning. It draws on French philosopher Michel Foucault's writings on sexuality and his notion that bodies are given meaning by discourse and social structures of knowledge and power. The binary oppositions (man/woman, gay/straight) on which discourse, and thus subjectivity, are founded are revealed to be not fixed, but fluid, fictional – and can, therefore, be destabilised. For a feminist who liked playing with words, the radical potential in this appealed.

The first book to grab me was the Butler, and this was mainly because of the resonance of the sepia-toned image on the cover of my Routledge edition, which mirrored that photograph from my childhood. It shows a young boy standing next to a young girl, both wearing dresses complete with frills and ruffles. The words inside, which introduce in Butler's inimitable style the idea of gender as performance, have best been summarised, I think, by the internet meme of a photograph of Butler delivering a lecture, overlaid with the words "Gender – yer 'doing' it".

But it was the introduction to Sedgwick's Epistemology of the Closet, titled Axiomatic, that I devoured in one sitting. In the book, the American academic, who died of breast cancer in 2009 aged 58, deploys erudite and playful readings of texts by Oscar Wilde, Henry James and Marcel Proust to interrogate assumptions about the stability of sexual identity and how language works to define a homo/heterosexual binary. She writes: "An understanding of virtually any aspect of modern western culture must be not merely incomplete but damaged in its central substance to the degree that it does not incorporate a critical analysis of modern homo/heterosexual definition."

In the introduction, Sedgwick presents axioms – "assumptions and conclusions from a long-term project of anti-homophobic analysis" – that inform her book's project. Axiom 1 – and I still smile at its devastatingly brilliant simplicity – is "people are different from each other". To prove this obvious but overlooked fact, Sedgwick lists a series of things "that can differentiate even people of identical gender, race, nationality, class, and 'sexual orientation' – each one of which, however, if taken seriously as pure difference, retains the unaccounted-for potential to disrupt many forms of the available thinking about sexuality".

It's worth quoting a few in full: "Even identical genital acts mean very different things to different people"; "Sexuality makes up a large share of the self-perceived identity of some people, a small share of others'"; "Some people like to have a lot of sex, others little or none"; "Many people have their richest mental/emotional involvement with sexual acts that they don't do, or even don't want to do."

The "puzzle" is why, instead of seeing people and relationships in this wonderfully multitudinous way, just one: "the gender of object choice – emerged from the turn of the century, and has remained as the dimension denoted by the now ubiquitous category of 'sexual orientation'." In other words, you are not who you have sex with, but that's all people seem to care about, with often devastating consequences.

So why did it strike such a chord with this straight girl? Well, Sedgwick herself married a man, Hal Sedgwick, though she would not have used the term "straight", seeing sexual identity as a continuum rather than a category. And if queer is anything, it's a retort to the idea that your sexual (or any) identity must define you in a static, limiting way, and above all, that it may be used to vilify you.

I saw the potential, then, in queer as it was intended: as a verb, to queer, rather than a noun, which could be applied to any number of ways in which society was structured so that only certain people, and voices, were valued. As Sedgwick writes elsewhere, "queer is a continuing moment, movement, motive – recurrent, eddying, troublant". It is "the open mesh of possibilities, gaps, overlaps, dissonances and resonances, lapses and excesses of meaning when the constituent elements of anyone's gender, of anyone's sexuality aren't made (or can't be made) to signify monolithically". Queer is "relational". It is "strange". To think, read or act queerly is to think across boundaries, beyond what is deemed to be normal, to jump at the possibilities opened up by celebrating marginality, which in itself serves to destabilise the mainstream.

The (predominantly US-based) activism alongside queer theory – born out of a frustration with lesbian and gay movements that were perceived as assimilationist, seeking the approval of dominant heterosexual society rather than challenging it – was intentionally provocative and confrontational. Groups such as Queer Nation staged kiss-ins, with slogans such as "Two, four, six, eight! How do you know your kids are straight?" and "We're here! We're queer! Get used to it!".

I loved this attitude. I still do. It informs my politics, and my journalism, in that I believe difference, diversity and deviance are strengths, not weaknesses. It also rehabilitated Robert in my eyes. When I think of me-as-Robert now, it is with a hint of defiance, rather than confusion, let alone shame. As Sedgwick said when appalled conservative commentators rejected her queer reading of literary greats: "Read any Sonnets lately? You dip into the Phaedrus often? To invoke the utopian bedroom scene of Chuck Berry's immortal aubade: Roll over, Beethoven, and tell Tchaikovsky the news."