It took me quite a while before I overcame my aversion to Blackwell's bookshop on Charing Cross Road, after it opened in 1998. One thing most Oxford undergraduates of my generation had in common was their "Blackwell's Bill". Often in excess of a thousand pounds, the bill was a measure of one's intellectual seriousness. Rumour had it that there were mysterious communications between the university and the bookshop, meaning you wouldn't be allowed to graduate until you had paid off your bill in full.

So, although I had long ago cleared my debt, I always felt anxious and undergradish and obscurely burdened on entering the Charing Cross Road branch. But when I finally started to go regularly, I discovered one of the best philosophy sections in London. The high bookshelves radiated around a central column as if they were the petals on a great flower. Living philosophers were stocked almost entire.

I took my English degree during the bitter final engagements of the Theory Wars. "Continental philosophy" was forbidden fruit. Perhaps because of this, it became extremely enticing to me, and has remained so. Also, I found it extremely convincing.

Perhaps the first book I bought from the philosophy section was Deleuze and Guattari's A Thousand Plateaus: Capitalism and Schizophrenia. It was one of the oddest things I had ever read - and I had made a point of seeking out odd books. But once I started to decode its language, I went back for more.

At this time, I was beginning to work on the novel that ended up as Journey into Space. I knew I wanted space to overwhelm the book, but I was finding it very difficult to think about what space is. I had heard of the French philosopher Henri Bergson (1859-1941), but knew very little about him. Most of the references I'd come across were slighting. Bergson didn't deal in the Wittgenstein-derived examination of common speech. He was a metaphysician - no practical use whatsoever. In fact, philosophically unfounded, nonsensical, etc.

I'm fairly sure when I picked up Bergsonism I first checked in the index for "Space" (yes, quite a few mentions), and then turned to the translators' introduction. The following words, I think, were what convinced me this was my kind of stuff. Deleuze is explaining his desire to escape the scholasticism of postwar French academic philosophy: "My way of getting out of it at that time was, I really think, to conceive of the history of philosophy as a kind of buggery or, what comes to the same thing, immaculate conception. I imagined myself getting on to the back of an author, and giving him a child, which would be his and which would at the same time be a monster."

The main text of Bergsonism is only a hundred pages long. I read it fast, and found it revelatory. Here is just one sentence: "If the real is said to resemble the possible, is this not in fact because the real was expected to come about by its own means, to 'project backwards' a fictitious image of it, and to claim that it was possible at any time, before it happened?"

This argument, when followed through, is a tremendous liberation from a commonsensical view of just about anything. What Bergsonism demonstrated to me, very succinctly, was that it is worth pursuing an entirely metaphysical philosophy, because there are discoveries to be made in this realm. How do human lives relate to time? How do our memories exist both within and without this element? What does it mean that something happened? A lot of people feel no need to call their version of reality into question. I do, because I have always been convinced that I was wrong - that I wasn't seeing the thing well enough.

It is very difficult to keep Bergson's conceptions of time and space in mind, because they are paradoxical and counter-intuitive. That is why I reread sections of Bergsonism more regularly than any other book - to remind myself that Deleuze-Bergson's monstrous way of thinking about the universe is more accurate and truthful than my exhausted default.

“Bergsonism" by Gilles Deleuze is published by MIT Press (£14.95 paperback)
Toby Litt's latest novel, "Journey into Space", is published by Penguin (£7.99)