Joaquin Phoenix is not here to preach

• Joaquin Phoenix poised to play the Joker in new standalone movie

Instead, he sits, slouching, grimacing – and cracking the odd deadpan joke – in front of a room full of journalists, all awaiting his gospel. The cameras are off.

“I get so sick of the sound of my own voice,” he says, as if with a heavy heart, knowing that his lifeblood is about to be drained from him once again. As soon as he gets going, however, he reminds us why we’re all so eager to get in a room with him in the first place.

In part, it’s because we expect him to say something strange, to bristle at questions, to cancel interviews (two out of three ain’t bad). But it’s also because he’s deeply passionate about his work, and it shows. It’s why his colleague (and current girlfriend) Rooney Mara identifies him as “the most gifted actor I’ve ever worked with”.

The whole experience makes it rather fitting that the role he’s here to talk about is that of Jesus Christ, a man who sacrificed himself for a greater good. The interview is Joaquin Phoenix’s crucifixion.

“I definitely hesitated,” he says of the decision to portray one of the most widely known figures in history, “[but] the second time I started reading [the script] I found it to be really emotional.”

The film’s feminist through-line was also a significant factor in his decision. Director Garth Davies (Lion) and writers Helen Edmunson and Philippa Goslett reposition Mary Magdalene as the 13th apostle, correcting the myth, still perpetuated today, that she was a prostitute.

“It’s unf***ingbelievable that it’s still happening,” Phoenix says of the misconception. “You know, in the bible you have two options of women, you either have the virgin or you have the prostitute, the sinner.”

In the 1960s, the Catholic church ruled that Pope Gregory I's declaration, in 591, that she was a prostitute to be incorrect, and in 2016 identified her as "apostle of the apostles". But her name still bears smatterings of mud.

“Somebody made that decision to exclude her observations and feelings about the life of Christ and her experience. There seems to have been an overt intention to exclude women from that process. And so, I think it’s totally relevant to what we still see today,” he says, alluding to, well, the entire history of gender relations.

Once he had signed up as Jesus, he was faced with the task of finding a way to add nuance to a role that has been played countless times before.

"Of course you approach something and you fear, like, everybody’s expectations, and that seems really daunting and overwhelming and, like, how can I do that?" he says. "And then I just had to remind myself that he was a man, and I had to try to find some personal connection in some way."

He speaks thoughtfully about the separation of Jesus the god and Jesus the man – the latter is more present than ever in Garth Davies’ depiction – and what the character can represent from a humanist perspective. He’s not a religious person himself.

“I just realised, for the crucifixion to be a real sacrifice and for it to mean something, means that he’s human and he has these human feelings,” he says. “He didn’t want to die, but he was willing.”

“It’s a time where, if you had a physical deformity or were mentally disabled, they thought that you were possessed by demons. And you were on the fringes, and I think kind of the power in some ways of what we were exploring was, here is this man that really saw you, and would touch you and look at you and validate you,” he says, “at a time where everyone in your community would shun you. And I thought that was such a beautiful idea.”

And Phoenix does indeed bring a stark humanity to Jesus – his eyes alone convey a kind of deep sadness, and a hint of fear – that, in the context of Christ’s role in the Bible, speaks volumes about the reality of the sacrifice that he made.

“I think part of his teaching was that you don’t have to be leader of a synagogue or a church leader to connect with that thing, whatever it is that you want to call it,” he says, in reference to a more spiritual representation of the kingdom of heaven, as portrayed in the film. “We all have access to it, we are all flesh and spirit. So I think it just, like, confirms in some ways what I’ve always naturally felt.“

The actor speaks reverentially of contemporary figures that work in the same vein as Jesus Christ, such as Helen Prejean, a New Orleans-based nun who served as spiritual advisor to death row inmates, and Reverend James Lawson, a civil rights activist who worked alongside Martin Luther King Jr in the 1960s. He has first-hand experience with the latter.

“He still teaches a workshop on non-violence in Los Angeles that I attend. He’s somebody who actually experienced people trying to kill him, and found the power not to react with violence. So, I think people like that were a real inspiration for me also.”

The mention of a non-violence workshop piques interest in the room – but just as we think there may be a salacious detail to be wrought, he begins to wax, with genuine sincerity, about the nature of human behaviour.

“I think that a lot of our aggression and violence are things that are learned, and we can train ourselves to react to things differently, and to find a way to communicate non-violently,” he says. “And when I say non-violently, sometimes I don’t mean literally, physically violent, sometimes just verbally violent.”

He’s famously a vegan, and his rhetoric suggests that it’s just one of the ways that he is attempting to limit the damage his existence has on the earth.

“Sometimes it feels very frustrating when you see the state of the world – I don’t know about you – but sometimes you feel overwhelmed. Like, oh f***, everywhere I turn there’s just violence and there’s hunger and disease and its overwhelming,” he says.

“And you think well, what can I do in my own life, how can I behave in my life... I have this expectation that other people are gonna solve these problems. And there’s nothing wrong with kind of encouraging that and being active politically, but there’s something I can do right now thats certainly going to affect the world and effect my world. So I want to try to learn how to do that.”

Soon, our time is up, and, despite his clear ambivalence for the process, it has been fruitful. It's only when he's asked more routine questions that his responses turn monosyllabic. His gaze cuts through me when I ask him if he is set to play the Joker, as has been reported in several in-the-know outlets in the US: "I dunno," he says.

His closing remarks, on using his platform to send out a message, give us a greater insight into his attitude towards his job, and the media cycle that goes hand in hand.

"I hope that people are affected by [my work] and it makes them think differently about the world," he says. "But I'm in no position to, like, suggest what motherf***ers want to do with their lives, or how they want to live their lives. Like, It’s not my job to teach someone something, but I have these experiences and they’re things that interest me and I hope that they inspire people to think differently about something that they might have thought they were familiar with. I think that's as much as I can do."

Mary Magdalene is out in UK cinemas on 16th March