During his flight home from what's seen as a highly successful visit to Africa, a journalist challenged Pope Francisabout the Roman Catholic Church's opposition to the use of condoms. The argument has always been that using condoms is an effective way of guarding against the transmission of the HIV virus and that the Church's position is unhelpful, to say the least. The pope, described as "visibly upset", said that the use of condoms was just a 'band-aid' solution to the problems of the continent.

I just don't get this. What's the Catholic Church got against condoms?

It's not just condoms. The Roman Catholic Church is opposed to all forms of artificial contraception. The ban is widely ignored in industrialised countries, but observed much more strictly in developing countries.

And the rationale for this is?

The Church's opposition to contraception was formalised in 1968 by Pope Paul VI in his encyclical Humanae Vitae ('Of Human Life') though previous popes and theologians had also spoken out against it. Pope Paul said that "each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life". The encyclical was in part a response to the advent of the birth control pill and following an earlier Pontifical Commission on Birth Control had been expected to liberalise the Church's teaching. One reason it didn't was that it would mean admitting previous popes had been wrong.  

I still don't get it. What's so wrong with contraception?

There are two issues, one more social and one a bit more theological. The social argument is that cutting the link between sex and procreation damages family life because it means sex can be recreational and consequence-free. The evidence is that the Church is on to something here, shown by high divorce rates and high rates of single motherhood in developed countries. However, the toothpaste is out of the tube on this one. The second argument is more fundamental: as Humanae Vitae says, "an act of mutual love which impairs the capacity to transmit life which God the Creator, through specific laws, has built into it, frustrates His design which constitutes the norm of marriage, and contradicts the will of the Author of life".

Fair enough, but I can't say I'm convinced.

Many Catholics aren't either. However, it has to be said that Catholics have thought much harder about this than Protestants and identified real issues about the boundless liberties Western society allows itself today.

Back to the condoms. Can't you use them to stop passing on HIV?

The short answer is, "probably". Humanae Vitae says that "the Church does not consider at all illicit the use of those therapeutic means necessary to cure bodily diseases, even if a foreseeable impediment to procreation should result there from". It wasn't referring to condoms, but there's a bit of leeway there. And in 2010 Pope Benedict said in answer to a question about condoms and the Church: "It of course does not see it as a real and moral solution. In certain cases, where the intention is to reduce the risk of infection, it can nevertheless be a first step on the way to another, more humane sexuality."

So, no problem then?

If only. In fact there are several. One is that if someone knows that they are HIV positive and if they consent to use a condom during intercourse it might reduce the risk of transmission. However, those are two very big ifs. Another is that while condoms are widely regarded as helpful against HIV, it's a huge mistake to imagine that they are a silver bullet. The controversial former director of the Harvard Center for Population and Development Studies, Dr Edward Green, made headlines in 2009 when he publicly backed Pope Benedict, saying that there was no correlation between condom use and falling rates of infection and that widespread condom availability just made people act in riskier ways. In a Washington Post article he wrote: "So what has worked in Africa? Strategies that break up... sexual networks – or, in plain language, faithful mutual monogamy or at least reduction in numbers of partners, especially concurrent ones."

That's incredible. So the Vatican's right?

Not, with respect, exactly. According to UN Aids, condoms are critical to their work – though they say particularly that they have "helped to reduce HIV transmission and curtailed the broader spread of HIV in settings where the epidemic is concentrated in specific populations" – eg sex workers and gay people.

What may be true is that widespread condom use is associated with more promiscuity, which is risky behaviour. And condoms are not always used properly and are not always effective, so HIV spreads. What seems to be the case is that condoms are effective against HIV transmission for each person who uses them, but for whole societies the evidence is not very good. However, at the moment there is effectively a blanket ban for Catholics. So faithful Catholics who know they are HIV positive or that their partners are can't use condoms either.

And what does Pope Francis think about that?

He is a pastor, not an ivory-tower academic. When he was asked about condom use on the plane, he said that such questions were "too small" in the context of hunger, a lack of access to drinkable water, slave labour, environmental degradation and war. When we no longer have these problems we can talk about condoms, he said: "I don't like doing casuistry when people are dying for a lack of water and hunger." He is theologically orthodox (which liberals often forget) and worries about modern family life and family breakdown, but he is very unlikely to get wound up about individuals who decide to use condoms to keep themselves safe.

I like Pope Francis.

Me too. Incidentally, did you know that the Catholic Church is the largest private provider of care to HIV/AIDS patients in the world?

Follow @RevMarkWoods on Twitter.