A pastor in Illinois has been making waves with a book that says it's OK for Christians to have sex before marriage.

Rev Bromleigh McCleneghan, a married mother of three and associate pastor for ministry with families at Union Church of Hinsdale, says single Christians can have sex as long as it's "mutually pleasurable and affirming".

In her book Good Christian Sex: Why Chastity Isn't the Only Option – And Other Things the Bible Says About Sex, she says being chaste is more about self-control and moderation than it is about abstinence. In an article for the Washington Post, she says: "I'd argue that we can be chaste – faithful – in unmarried sexual relationships if we exercise restraint: if we refrain from having sex that isn't mutually pleasurable and affirming, that doesn't respect the autonomy and sacred worth of ourselves and our partners."

And, she says: "There are those who feel that they are called to seasons of celibacy, or even years of celibacy, and if answering that call is life-giving and purposeful, then they should take it up as a spiritual discipline. But no call can be forced on an unwilling person, especially not if they find themselves single only by virtue of circumstance."

Needless to say, her views have been roundly condemned by conservatives. Pastor Greg Laurie of Harvest Christian Fellowship told the Christian Post McCleneghan was "misrepresenting God" and her teaching could push people away from him. Asked on her Facebook page whether there had been aggressive reactions to the book, McCleneghan replied, "Why yes, there have been." One commenter, Amy Quoshena, wrote: "You are leading many to hell with your book. You should be ashamed of yourself. It is written that sexual immorality is a sin and those who do burn in the lake of fire. Repent!!"

Full disclosure: I haven't read the book yet, so this isn't a review. However, the lines of her thinking are clear enough from what she's said and written. She's not advocating a sexual free-for-all, but she's critical of the idea that the only place for sexual expression is within marriage. Our bodies have needs, and meeting those needs with another person, even one to whom we aren't married, can be a deeply fulfilling experience. She points out the Bible's inconsistencies about sex and that some sex within marriage is coercive and abusive. Denying our bodies "the things they need for health and joy" is a bad thing, and "Denying the facts of our humanity seems like a theologically problematic move."

Where will this lead? One interviewer, Jonathan Merritt for RNS, asked her about polygamy and whether it could ever be "holy". Too patriarchal, she said. "Polyamory, though, as a sexual and romantic relationship between three or more consenting people? I don't know. I think it would be really hard insofar as intimacy is hard enough in a dyad, and mutuality would be well near impossible given the even more complicated power dynamics and the reality of sin. I think there's something really lovely about long-term monogamy that would be hard to capture with additional partners. But, just because something is outside my experience doesn't mean it's necessarily wrong."

The reason McCleneghan has attracted so much attention – much of it negative, but much of it very positive from people who feel she speaks for them – is that she's a pastor who has publically broken a Christian consensus about sex in a thoughtful and informed way. That doesn't, of course, mean that she's right, but it means Christians are talking about something really important in a more honest way than perhaps they were.

But is she right? At one level, it's fair enough to critique the idea that for Christians, a legal marriage ceremony is the sole criterion for deciding whether two people can have sex or not. At different times and in different places marriage has looked very different. And it's true, as well, to say that anyone who goes to the Bible for a "biblical" view of marriage has to explain away quite a few practices that don't look anything like what they might imagine.

Nevertheless, the settled position of the Church has been that monogamy is God's best design for human beings and that any other arrangement falls short of His perfect will. As Christians are called to the highest form of discipleship, that's what we should aim for. And here, in a nutshell, are my reservations about her arguments.

1. It's all too convenient

Yes, most of us have physical desires. And the idea that if we are single we need not, in fact, restrain them, and can indulge them to our hearts' content as long as we aren't hurting anyone and it's all consensual, is terribly, terribly attractive. We should be deeply suspicious of any interpretation of Scripture or tradition that lets us do exactly what we want.

2. Our bodies are not our masters

The fact that we have physical cravings doesn't mean we have to satisfy them. Paul addresses this in 1 Corinthians 6:13, when he quotes the proverb "Food for the stomach, and the stomach for food" – in other words, sexual pleasure is as free of moral content as eating a meal. But God will destroy them both, he says, and: "The body, however, is not meant for sexual immorality but for the Lord, and the Lord for the body." Food and sex are different.

3. You can't separate minds and bodies

At least, many people can't. It's wrong to generalise, and Christians are on shaky ground when they claim there are always spiritual consequences to sexual relations outside marriage. What to one person is a profoundly significant act is to another no more important than brushing their teeth. But what seems clear from the language of Scripture is that there's a deep connection between physical and spiritual union that is best expressed through life-long, committed monogamy.

A book that gets Christians talking about sex is probably a good thing, as far as it goes. And the Church in today's Western world, where sex before marriage is normal, has got to have something more to say to young people in particular than just, "Thou shalt not." One thing it might say is, "This is the Church's teaching, but if you choose not to follow it you don't put yourself beyond the grace of God or outside the Church's fellowship." But should the Church revise its teaching? No.

Follow Mark Woods on Twitter: @RevMarkWoods