A genius with the answers to the financial crisis? Or the Borat of philosophy? The cultural theorist talks about love, sex and why nothing is ever what it appears to be

Slavoj Žižek doesn't know the door number of his own apartment in Ljubljana. "Doesn't matter," he tells the photographer, who wants to pop outside. "Come back in through the main door, and then just think in terms of politically radical right; you turn from left to right, then at the end, right again." But what's the number, in case he gets lost? "I think it's 20," Žižek suggests. "But who knows? Let's double check." So off he pads down the hallway, opens his door and has a look.

Waving the photographer off, he points in the distance across the Slovenian capital. "Over there, that's a kind of counter-culture establishment – they hate me, I hate them. This is the type of leftists that I hate. Radical leftists whose fathers are all very rich." Most of the other buildings, he adds, are government ministries. "I hate it." Now he's back in the living room, a clinically tidy little sliver of functional space lacking any discernible aesthetic, the only concessions being a poster for the video game Call Of Duty: Black Ops, and a print of Joseph Stalin. Žižek pours Coke Zero into plastic McDonald's cups decorated in Disney merchandising, but when he opens a kitchen cupboard I see that it's full of clothes.

"I live as a madman!" he exclaims, and leads me on a tour of the apartment to demonstrate why his kitchen cabinets contain only clothing. "You see, there's no room anywhere else!" And indeed, every other room is lined, floor to ceiling, with DVDs and books; volumes of his own 75 works, translated into innumerable languages, fill one room alone.

If you have read all of Žižek's work, you are doing better than me. Born in 1949, the Slovenian philosopher and cultural critic grew up under Tito in the former Yugoslavia, where suspicions of dissidence consigned him to academic backwaters. He came to western attention in 1989 with his first book written in English, The Sublime Object of Ideology, a re-reading of Žižek's great hero Hegel through the perspective of another hero, the psychoanalyst Jacques Lacan. Since then there have been titles such as Living in the End Times, along with films – The Pervert's Guide To Cinema – and more articles than I can count.

By the standards of cultural theory, Žižek sits at the more accessible end of the spectrum – but to give you an idea of where that still leaves him, here's a typical quote from a book called Žižek: A Guide for the Perplexed, intended to render him more comprehensible: "Žižek finds the place for Lacan in Hegel by seeing the Real as the correlate of the self-division and self-doubling within phenomena."

At the risk of upsetting Žižek's fanatical global following, I would say that a lot of his work is impenetrable. But he writes with exhilarating ambition and his central thesis offers a perspective even his critics would have to concede is thought-provoking. In essence, he argues that nothing is ever what it appears, and contradiction is encoded in almost everything. Most of what we think of as radical or subversive – or even simply ethical – doesn't actually change anything.

"Like when you buy an organic apple, you're doing it for ideological reasons, it makes you feel good: 'I'm doing something for Mother Earth,' and so on. But in what sense are we engaged? It's a false engagement. Paradoxically, we do these things to avoid really doing things. It makes you feel good. You recycle, you send £5 a month to some Somali orphan, and you did your duty." But really, we've been tricked into operating safety valves that allow the status quo to survive unchallenged? "Yes, exactly." The obsession of western liberals with identity politics only distracts from class struggle, and while Žižek doesn't defend any version of communism ever seen in practice, he remains what he calls a "complicated Marxist" with revolutionary ideals.

To his critics, as one memorably put it, he is the Borat of philosophy, churning out ever more outrageous statements for scandalous effect. "The problem with Hitler was that he was not violent enough," for example, or "I am not human. I am a monster." Some dismiss him as a silly controversialist; others fear him as an agitator for neo-Marxist totalitarianism. But since the financial crisis he has been elevated to the status of a global-recession celebrity, drawing crowds of adoring followers who revere him as an intellectual genius. His popularity is just the sort of paradox Žižek delights in because if it were down to him, he says, he would rather not talk to anyone.

You wouldn't guess so from the energetic flurry of good manners with which he welcomes us, but he's quick to clarify that his attentiveness is just camouflage for misanthropy. "For me, the idea of hell is the American type of parties. Or, when they ask me to give a talk, and they say something like, 'After the talk there will just be a small reception' – I know this is hell. This means all the frustrated idiots, who are not able to ask you a question at the end of the talk, come to you and, usually, they start: 'Professor Žižek, I know you must be tired, but …' Well, fuck you. If you know that I am tired, why are you asking me? I'm really more and more becoming Stalinist. Liberals always say about totalitarians that they like humanity, as such, but they have no empathy for concrete people, no? OK, that fits me perfectly. Humanity? Yes, it's OK – some great talks, some great arts. Concrete people? No, 99% are boring idiots."

Most of all, he can't stand students. "Absolutely. I was shocked, for example, once, a student approached me in the US, when I was still teaching a class – which I will never do again – and he told me: 'You know, professor, it interested me what you were saying yesterday, and I thought, I don't know what my paper should be about. Could you please give me some more thoughts and then maybe some idea will pop up.' Fuck him! Who I am to do that?"

Žižek has had to quit most of his teaching posts in Europe and America, to get away from these intolerable students. "I especially hate when they come to me with personal problems. My standard line is: 'Look at me, look at my tics, don't you see that I'm mad? How can you even think about asking a mad man like me to help you in personal problems, no?'" You can see what he means, for Žižek cuts a fairly startling physical figure – like a grizzly bear, pawing wildly at his face, sniffing and snuffling and gesticulating between every syllable. "But it doesn't work! They still trust me. And I hate this because – this is what I don't like about American society – I don't like this openness, like when you meet a guy for the first time, and he's starting to tell you about his sex life. I hate this, I hate this!"

I have to laugh at this, because Žižek brings up his sex life within moments of our first meeting. On the way up in the lift he volunteers that a former girlfriend used to ask him for what he called "consensual rape". I had imagined he would want to discuss his new book about Hegel, but what he really seems keen to talk about is sex.

"Yeah, because I'm extremely romantic here. You know what is my fear? This postmodern, permissive, pragmatic etiquette towards sex. It's horrible. They claim sex is healthy; it's good for the heart, for blood circulation, it relaxes you. They even go into how kissing is also good because it develops the muscles here – this is horrible, my God!" He's appalled by the promise of dating agencies to "outsource" the risk of romance. "It's no longer that absolute passion. I like this idea of sex as part of love, you know: 'I'm ready to sell my mother into slavery just to fuck you for ever.' There is something nice, transcendent, about it. I remain incurably romantic."

I keep thinking I should try to intervene with a question, but he's off again. "I have strange limits. I am very – OK, another detail, fuck it. I was never able to do – even if a woman wanted it – annal sex." Annal sex? "Ah, anal sex. You know why not? Because I couldn't convince myself that she really likes it. I always had this suspicion, what if she only pretends, to make herself more attractive to me? It's the same thing for fellatio; I was never able to finish into the woman's mouth, because again, my idea is, this is not exactly the most tasteful fluid. What if she's only pretending?"

He can count the number of women he has slept with on his hands, because he finds the whole business so nerve-racking. "I cannot have one-night stands. I envy people who can do it; it would be wonderful. I feel nice, let's go, bang-bang – yes! But for me, it's something so ridiculously intimate – like, my God, it's horrible to be naked in front of another person, you know? If the other one is evil with a remark – 'Ha ha, your stomach,' or whatever – everything can be ruined, you know?" Besides, he can't sleep with anyone unless he believes they might stay together for ever. "All my relationships – this is why they are very few – were damned from the perspective of eternity. What I mean with this clumsy term is, maybe they will last."

But Žižek has been divorced three times. How has he coped with that? "Ah, now I will tell you. You know the young Marx – I don't idealise Marx, he was a nasty guy, personally – but he has a wonderful logic. He says: 'You don't simply dissolve marriage; divorce means that you retroactively establish that the love was not the true love.' When love goes away, you retroactively establish that it wasn't even true love." Is that what he did? "Yes! I erase it totally. I don't only believe that I'm no longer in love. I believe I never was."

As if to illustrate this, he glances at his watch; his 12-year-old son, who lives nearby, will be arriving shortly. How is this going to work when he gets here? Don't worry, Žižek says, he's bound to be late – on account of the tardiness of his mother: "The bitch who claims to have been my wife." But weren't they married? "Unfortunately, yes."

Žižek has two sons – the other is in his 30s – but never wanted to be a parent. "I will tell you the formula why I love my two sons. This is my liberal, compassionate side. I cannot resist it, when I see someone hurt, vulnerable and so on. So precisely when the son was not fully wanted, this made me want to love him even more."

By now I can see we're not going to get anywhere near Žižek's new book about Hegel, Less Than Nothing: Hegel and the Shadow of Dialectical Materialism. Instead, he tells me about the holidays he takes with his young son. The last one was to the Burj Al Arab hotel, a grotesque temple to tacky ostentation in Dubai. "Why not? Why not? I like to do crazy things. But I did my Marxist duty. I got friendly with the Pakistani taxi driver who showed to me and my son reality. The whole structure of how the workers there live was explained, how it was controlled. My son was horrified." This summer they are off to Singapore, to an artificial island with swimming pools built on top of 50-storey skyscrapers. "So we can swim there and look down on the city: 'Ha ha, fuck you.' That's what I like to do – totally crazy things." It wasn't so much fun when his son was younger. "But now, we have a certain rhythm established. We sleep 'til one, then we go to breakfast, then we go to the city – no culture, just consumerism or some stupid things like this – then we go back for dinner, then we go to a movie theatre, then we play games 'til three in the morning."

I wonder what all Žižek's earnest young followers will make of this, and worry they will be cross with me for not getting anything more serious out of him. But to Žižek, Dubai tells us just as much about the world as a debate about the deficit, say, ever can. When his sweet-looking, polite young son arrives, I try to steer Žižek on to the financial crisis, and to the role his admirers hope he will play in formulating a radical response.

"I always emphasise: don't expect this from me. I don't think that the task of a guy like me is to propose complete solutions. When people ask me what to do with the economy, what the hell do I know? I think the task of people like me is not to provide answers but to ask the right questions." He's not against democracy, per se, he just thinks our democratic institutions are no longer capable of controlling global capitalism. "Nice consensual incremental reforms may work, possibly, at a local level." But localism belongs in the same category as organic apples, and recycling. "It's done to make you feel good. But the big question today is how to organise to act globally, at an immense international level, without regressing to some authoritarian rule."

How will that happen? "I'm a pessimist in the sense that we are approaching dangerous times. But I'm an optimist for exactly the same reason. Pessimism means things are getting messy. Optimism means these are precisely the times when change is possible." And what are the chances that things won't change? "Ah, if this happens then we are slowly approaching a new apartheid authoritarian society. It will not be – I must underline this – the old stupid authoritarianism. This will be a new form, still consumerist." The whole world will look like Dubai? "Yes, and in Dubai, you know, the other side are literally slaves."

There is something inexplicably touching about all Žižek's mischievous bombast. I hadn't expected him to be so likable, but he really is hilariously good company. I had hoped to find out if he was a genius or a lunatic – but I fear I leave none the wiser. I ask him how seriously he would recommend we take him, and he says he would rather be feared than taken for a clown. "Most people think I'm making jokes, exaggerating – but no, I'm not. It's not that. First I tell jokes, then I'm serious. No, the art is to bring the serious message into the forum of jokes."

Two years ago his front teeth came out. "My son knows I have a good friend; none of us is gay, just good friends. So when he saw me without teeth, he said: 'I know why.' My son! He was 10! You know what he told me? Think, associate, in the dirtiest way." I think I can guess. "Yes! Sucking! He said my friend complained that my teeth were in the way." Žižek roars with laughter, great gales of paternal pride.

"And you know what was tragicomic? After he told me this, he said: 'Father, did I tell this joke well?'"

A 24-hour launch event for Less Than Nothing takes place on 15 June at Cafe Oto, London. versobooks.com.