Yesterday I went to a B&Q hardware store. Full disclosure: it's not my natural habitat, but my need for a lightbulb was pressing. Faced with a frankly bewildering range, I asked for help. To my surprise lightbulb advice was available at the Paint Mixing Desk. I don't know what image pops into your head when I say 'Paint Mixing Desk', but it was hi-tech. Think Mission Control at NASA, and you won't be far off. While mixing a bespoke pot of emulsion, the woman behind the desk talked me through wattage, lumens, bayonet caps, all of that. As we talked, another female shop assistant swept by in a forklift, deftly handling a massive pallet of sealant.

Quite naturally, my mind turned to theology – I should explain, I write about philosophy, so when I go to B&Q big ideas are never far behind.

I asked myself, as evangelicals so often do, what would John Piper say? Women were speaking authoritatively and operating heavy machinery like it was the most natural thing in the world, and in a hardware store of all places. Was this a full-scale assault on God's vision of masculinity, or just another Monday morning in the paint aisle?

In reality, my early morning shopping trip was nothing out of the ordinary. But it made me think about how everyday events might be interpreted by theologians of gender.

The 2018 THINK conference is about to make gender a hot topic. Andrew Wilson, a London pastor, trailed the conference as a chance to rethink the theology of women and men. Speaking to Premier Christianity, Wilson acknowledged that his views on women had changed. 'I would have been in a position 10 years ago when we did not have women on the preaching rota. And we do now – in both the churches I serve.' He wants a new emphasis on 'complementarity', a theology which recognises natural differences between women and men, as well as equality. Apparently, Wilson wants to use scientific studies of women and men to help Christians understand gender differences.

Alastair Roberts is a main speaker at the event. The interesting thing is that while this approach to theology sounds quite reasonable, Roberts quickly gets quite controversial.

Roberts' view of women and men is something like this: he thinks that men are more inclined towards technology, whereas women are more inclined towards people. He thinks that men are more likely to be interested in philosophical and theological topics, while women will naturally prefer discussion of art or personal issues. What's more, he thinks that men are physically and mentally suited for combat in a way that women are not.

Roberts thinks that these natural differences reflect God's plan. Specifically, he says that 'Scripture repeatedly presents the bearing of children and the faithful managing of a household as the primary form that women's vocations will take.' Roberts admits that there will be a few women who play a different role, but he think these women will be the exceptions to God's general plan.

In practice, this means that women are likely to play a very small role in some areas of life. In fact, there are areas where Roberts thinks women are unnecessary. For example, Roberts thinks that there is no need for women to contribute to theology. Equally, in tasks that are related to physical strength or technology women are also likely to play a small role.

Can women be persuaded to think about theology, or to develop a real interest in technology? Roberts thinks that efforts to encourage women in these areas are likely to be unhelpful. Encouraging women to enter the world of theology or technology sets most women up for failure, as areas like these simply don't play to women's natural strengths. Worse still, as women fail they will become frustrated and resentful, and they will try to stop men succeeding at the things they naturally find fulfilling. In fact, Robert thinks this kind of resentment is one of the features of feminism.

The funny thing about Roberts' view is how quickly it moves from the uncontroversial idea that men and women are different, to the much more provocative idea that, men and women should lead very different kinds of lives.

What does Roberts' view mean in practice? What if my daughter wants to study theoretical physics at university? Do I say 'Go for it!' or do I say, 'Hang on a minute, you're a women, chances are you're not cut out for physics. You'll just get frustrated, resentful and turn into a feminist – no one wants that.' Or perhaps, 'OK, a university is a good place to meet a man with wallet bearing hips. It's never too soon for a woman to start thinking about settling down, faithfully managing a household, and childbearing.'

Of course, I'm sure Roberts would never say anything quite that crass – no one wants to be called sexist. But Christian men do, and if you don't believe me google #thingsonlychristianwomenhear and #thingsonlyblackchristianwomenhear. What's more, people don't need to say these things to communicate these kinds of prejudices.

The other strange thing is that in some ways Roberts doesn't think that men and women are complementary at all. Roberts thinks that men and women naturally make friends in very different ways. Therefore, he thinks that including women in male friendships is 'a threat to many male groups'.

Roberts' view of women and men turns my experience in the hardware store into a big problem. I, a man, had to rely on a woman to explain technology. A female shop assistant had to speak to me about issues that were nothing to do with her relationships. A woman driving a forklift was doing a job requiring physical strength. And why weren't these women raising children and faithfully managing the home? If Roberts is right, the whole situation was an unholy mess.

The idea that men and women are different is hardly controversial. But Roberts seems to imagine a world where most scientists are men, and most women are at home. That sounds more like middle-class white America in the 1950s than heaven.

If women and men are truly complementary, surely that means that we should serve God together in all areas: bringing up children, making laws, understanding creation, making music, governing the home and the church, thinking about theology.

Roberts and Wilson are free to call their new theology whatever they want. But if their ideas tend to exclude women from any area of life, then they have failed to achieve genuine complementarity.

Dr Robin Bunce is a historian of ideas based at Homerton College, University of Cambridge. He has written on politics and contemporary culture for the Huffington Post, the Guardian, the Independent, and the New Statesman.