Professor Rae Langton seems a little bemused to be the subject of an interview. “Why me?” she asks, as we hurry across the chilly Newnham quad. I'm taken aback by her lack of self-importance.

Currently a philosophy fellow here in Cambridge, Langton's worked at universities around the globe (MIT, Princeton, Sheffield and Edinburgh, to name but a few). She's published over 60 articles, and two books. She's written for the New York Times. She's submitted evidence to the Leveson inquiry. Recently, Prospect magazine ranked her as one of its top fifty world thinkers of 2014. Her work, particularly that on pornography and hate speech, has captured attention both inside and outside of academia. She's garnered a reputation as one of the top philosophers on the planet. Very few academics have a Wikipedia page, but Langton is one of them.

The philosophy fanboy inside me rushes to tell her all of this and more, but I suppress my instincts and try to play it cool. We get into the Newnham fellows' common room and sit, enjoying the warmth, the armchairs engulfing us. I begin by asking about Langton's background. She tells me that she was born and raised in India: “My parents were evangelical missionaries. I was at boarding school in the South of India from the age of five until the age of eighteen.” It wasn't until after school, when Langton moved to Australia and began to study at the University of Sydney, that she first encountered the subject that would form such a large part of her life.

Langton chanced into philosophy. “I wanted to do English, drama and biology and they wouldn't let me do biology, and so I did philosophy, not knowing what it was. I had no self knowledge at all; I fell into it completely by accident." 

Langton's religious background explains part of philosophy's initial appeal to her. Philosophy provided a means for structuring several doubts she was having about her faith. “It was really marvellous to be reading someone like Bertrand Russell – unlike the happy agnostics who I was surrounded by in Australia, you could see Russell felt there was something sad about God not being there. You felt he was shaking his fist at God for not existing.”

Philosophy helped Langton cope with a rejection of the Christianity she had been raised with. She openly voices her resentment of some aspects of religion: “At that point, what I found most difficult to maintain was the belief that a lot of good people were going to Hell... What I now find one of the most regrettable things about religion is that it tries to say that religion and ethics are one, that there would be no moral laws if it were not for God dictating them.”

Talking about analytic and continental philosophy (she is “definitely an analytic philosopher”), I get the sense from Langton that she thinks there is something dangerous about pigeonholing philosophers; she attributes some of the gender imbalance within academic philosophy, for example, to a stereotype that has “the ideal philosopher” reclining pipe in hand, beard on chin. As she puts it: “when you think of a philosopher, you don't think of someone who looks like me.”

The sheer volume of Langton's work means it's impossible to discuss all of it. I decide to steer conversation away from the serious metaphysics – more for my own sake than the reader's – and speak instead about her work on pornography, given that it's what she's best known for outside of those fields.

For Langton, pornography is separate from general erotica; unlike some erotic material, it degrades or objectifies women. She thinks that certain liberal political philosophers' views on pornography are “rosy and idealistic”, that they see it as something that must be defended against hordes of prudish moralists. Langton is known for her interpretation of Catharine MacKinnon's claim that pornography silences women; she uses ideas in the philosophy of language to show that pornography could literally stop women doing things with their words. Women's utterances of 'no' could, for some hearers, fail to count as refusal of consent, even when they are meant that way.

Langton's views have had a profound impact on the way philosophers treat pornography and hate speech; it seems conceivable that they could lead to real legislative change. I ask her whether she thinks philosophers have a role to play in changing the world. She seems cautiously optimistic about their chances: “Almost any question has its philosophical side, when you think about it, and I do think philosophers can contribute – as some of us have been doing – to debates about media ethics, racism and sexism, and free speech – the Leveson Inquiry being one recent example. So yes, philosophy could perhaps have more of an effect on the 'real world'. Just as importantly, the 'real world' could have more of an effect on philosophy; we need to have real people in mind, in our philosophical theorizing.”

One such example of 'real world' interaction seems to me to be the recent consent workshops. Langton confesses that she doesn't know a huge amount about them, but that what she has heard has been exceedingly positive: “You can’t tell, just from the armchair, whether consent workshops are a good idea, and talking about sex is often fraught and awkward. But when you get out of the armchair and learn that levels of sexual harassment and assault are way too high, levels of reporting are way too low, and many of us have a far from perfect idea of what legal consent involves, what most rapes are like, or even what our institution’s harassment policies are – well, there’s a problem that needs addressing.

"I gather that the workshops understand consent as 'active and willing participation in sexual activity', which cannot be assumed and 'means that both parties had the freedom and capacity to make the choice'. That sounds like a great start to me.”

By the time it comes to my exit, my calm veneer has dissolved. I abandon restraint as I thank her; I think the word 'honour' slips out. We both cringe, and I'm struck once again by just how down to earth Rae Langton is. It's rare to meet someone who has left such a large mark on the world; it's rarer still to meet someone so unaware of it.