Every Christian knows that when we die, though our bodies might be buried or cremated, our souls go to heaven. At some point something else happens involving resurrection and the Last Judgment, but that whole thing is rather odd and we tend to avoid the subject. Whatever lies after death is essentially mysterious, but we assume that – since our bodies clearly aren't involved, being dead – it has something to do with whatever's left. Call it the soul, call it the spirit. Whatever, from the point of view of eternity, bodies aren't really important.

Only, according to theologian Paula Gooder, pretty much all of this is wrong.

She's the author of Body: Biblical spirituality for the whole person (SPCK). In it she says we've imbibed a view of the body that says it's inherently bad or inferior. What really matters is our inner being, and the outer being – the body – has nothing to do with our relationship with God. And that isn't remotely what the Bible teaches.

Gooder, Theologian in Residence at Bible Society, recently gave a lecture at St Paul's Cathedral in which she expanded on her ideas.

She argued that we get our mistaken beliefs about the body from a misreading of the Apostle Paul, combined with ideas from the Greek philosopher Plato. In Plato's thinking, the soul and the body are opposites. The soul enters the body to animate it and leaves it at death. He even described the body as "the coffin of the soul". Later Christian theology drew on him and led to us seeing Paul through Plato's eyes. So the idea grew up that for Paul, the body was something to be rejected or despised – not least in its sexual aspect. Not so at all, says Gooder. Actually, Paul is very much in favour of bodies – and this really matters, particularly in today's world where we seem to be obsessed by them in quite an unhealthy way. 

Gooder has two teenage daughters, and decided to write her book after thinking about the sort of pressures they were facing. She says: "As I was looking at them, I began to yearn for a Christian voice that could come and speak passionately about what we think beautiful bodies really look like." She doesn't claim to be the only such voice, but she wrote the book to rebalance the Christian view of body and soul.

And one of the things she asks us to question is how we make that distinction. We tend to merge ideas into each other in a way Paul himself doesn't, and set them up in opposition to each other. So Paul talks about 'body' and 'flesh' and we think he's talking about the same thing – and he talks quite negatively about 'the flesh', characterised as the part of our nature that pulls us away from God. But, says Gooder, he uses different words deliberately, and when he talks about bodies he's usually positive. It's the same with 'soul' and 'spirit'. The 'soul' (psyche, in Greek) is used to describe the whole person, "that which makes a person alive" – and it includes the body. Spirit, on the other hand, is "that which comes from God; it's that which entwines with God's Spirit, it's the Godward part of us".

All of this is to say that for Paul, we are not souls inhabiting bodies – we are souls and bodies. He wasn't, like Plato, a dualist. And Gooder says: "Within dualism there are things that are only ever good and only ever bad. Part of the essence of Paul is that he believes in redemption. There's nothing irredeemable. There is not one category that's good, and another bad."

Instead, she says, Paul believes there are things that are part of this world, and things that are part of the world to come – and bodies are in both. In his great chapter on resurrection, 1 Corinthians 15, he puts bodies – resurrected, changed and transformed bodies – at the heart of his theology. So the idea that bodies are just discarded when we die is just wrong. Whatever heaven is, we will be embodied there rather than just being free-floating mental entities.

But we need to be careful how we think about resurrection, Gooder says. "If you were to ask most people what a resurrection body might be like, people have a lovely image, that everything you don't like about your body now will be gone: you'll be the Barbie and Ken of the resurrection world. There's no evidence in Bible at all that that is the vision of resurrection." Rather, she says, there are "continuities and discontinuities" – just as Jesus still bore the marks of his crucifixion, but was still unrecognisable to his disciples.

She argues that 1 Corinthians is a long "fugue" on the theme of bodies, reflecting as it does on the Church as a body, sex, food and the eucharist. "There's a strand running all the way through, which is about what you do with your body affects who you are, who you are affects what you do with your body, what you do with your body affects those around you, what you do with your body therefore affects who they are, who they are affects what they do with their bodies and round and round it goes."

And was Paul anti-sex? By no means. The famous line in 1 Corinthians 7:1 where he seems to say that "It is good for a man not to touch a woman" can only really be understood with quote marks around it – because he's quoting a question the Corinthians have asked him, and spends the rest of the chapter explaining why they're wrong. Gooder says: "Bear in mind that in the first century, in Judaism and in the wider Roman empire, sex was not about mutuality. Women were there to provide a service. Paul is the first ever person to say that sex should be mutual and should give pleasure. That is not the statement of someone opposed to sex." He ends by saying it's better not to get married, but: "He was writing in a world where woman had no choice. Men too – everyone gets married. Paul was the first one to say, no, you can choose. If you want to join me in the proclamation of the gospel, you might choose not to. Paul is not anti-sex, he's a radical forward thinker: sex should be mutural, it can give pleasure, and you can choose not to do it if you want to."

So what difference does it make if we take our bodies seriously? We need to have, says Gooder, an embodied spirituality that talks about our relationship with God in terms of our bodies as much as in terms of anything else. So, for instance: "We have to think very seriously and carefully about how we use our bodies in worship. If we engage with God through our bodies, what does our standing, our sitting, our kneeling or not not kneeling communicate about our spirituality?" It makes a difference to our prayer lives, too, if the assumption is that we go away in a room and pray "using only our spirits", which would not, says be her favourite pastime. "Care of our bodies should be as important in spirituality as anywhere else. If we're not taking care of our bodies, we aren't engaging in proper spiritual discipline."

In today's world we are obsessed by bodies, and particularly with their perfectibility. Diets and plastic surgery make perfect bodies seem within our reach. It might be argued that we need to recover a proper sense of the spiritual, rather than of the physical. But her point is that we shouldn't be separating the two.  

Another aspect of today's world is that for many people, much of it's lived online – inconceivable only a few years ago, let alone when Paul was writing. We can create personas for ourselves and interact on all sorts of levels with no physical presence at all. Would Paul approve? Probably not, Gooder thinks.

"For Paul, our bodies are so much a part of who we are that this view of the body would regard the desire to build an identity apart from a physical existence to be unsettling, destabilising and lacking in integration," she says. "It isn't that you shouldn't do it, but if you allowed a non-bodied existence to so take over your life that your bodied existence was seen to be less important, then you might find yourself to be less whole and at one with yourself than you might otherwise."

She adds: "Paul himself wrote letters so he too established a non-physical identity, but it was one that was linked integrally to his physical self."

And that physicality is part of our God-given nature, to be valued and respected as such. "For me, the difference that makes is that I have something to go back to my teenage girls with and say, you are beautiful, your bodies are beautiful. I think so, God thinks so and so does Paul – and the thing that makes them beautiful is the integration of heart and mind and soul and spirit and body. A truly integrated person is a beautiful person. I would love my teenage girls to hear that as a strong, passionate voice in Christianity."

Body: Biblical spirituality for the whole person (SPCK) by Paula Gooder is out now.