Governments use fiscal policy to promote various behaviours in their citizenry. Daniel Defoe recognised this centuries ago. “Not the Man in the Moon… not the Inspiration of Mother Shipton or the Miracles of Dr Faustus, things as certain as Death and taxes can be more firmly believed.”

Defoe was speaking about the power that immediate concerns, rather than otherworldly ones, have in motivating our behaviour. The threat of taxation, more than astrology, prophecy and tomfoolery, influences the way we behave. This is all the more so when the benefits make a real difference to our quality of life, such as among those who fall below the median income level.

What about fiscal policy makers themselves? Are they guided by astrology, prophecy or something more substantial?

Some have recently claimed that Conservative proposals to support married couples through fiscal incentives are misguided (government should not moralise) and unfair (why should the rich with no children get a tax break?). Some even blame them for promoting values that are rooted in Christian tradition, and thus imagine he is guided by (the equivalent of) astrology or psychics.

Such criticism notwithstanding, more politicians should be bold enough to promote the institution of marriage and the family – not necessarily because the Church says it’s God’s way of ordering creation (though it is) but because it’s the best way to build a strong society.

It is sad that some reject incentivising marriage, or even giving equal support to low income couples with children, because such measures are seen to be moralising. I have no doubt that this is, at least in part, because marriage is associated with Christianity and that Christianity is associated with moralising. Yet Christian values are good to follow not necessarily because they are Christian but because they are, well, good.

If the question is about fairness, as many believe it should be, why are parents who chose to marry (a valid choice like any other) penalised for doing so by our tax system?

Currently in the UK, fiscal policy intended to help single mothers, a wholly worthy cause, has created the odd situation where some couples are willing to live together but in separate homes because the tax system rewards them for doing so. On a national scale this is terribly wasteful, not only because shared housing is more efficient but because cohesive family life brings immeasurable (and often unmeasured) benefits both to individuals and society.

This regrettable situation means that if a single mother wanted to start living with a partner, she might well be financially worse off for doing so. You might assume the income in the household would increase but in actual fact the income may decrease in real terms because of the family’s loss of benefits. It’s not fair that she isn’t given this same support from society if she decides she wants to marry, especially not if either she or her husband want to stay at home with their children.

Unlike most other OECD countries, the UK treats couples in which one member stays at home to look after dependants quite unfairly. A recent study by the charity CARE compares OECD countries’ family fiscal polices with UK policy. Taxation of Married Families: How the UK Compares Internationally demonstrates not only that marriage is penalised in the UK, but that the tax burden on single earner married couples with young children on an average wage is 40% higher than the OECD average.

Perhaps we should talk not about fairness but about child poverty? It’s the same story. If we want to lift children out of poverty our current fiscal policy is sadly lacking. It is true that children in single parent families are at a great risk of living in poverty, but there are more children living in poverty in two parent families than in single parent homes and they should not be overlooked.

Marriage is a good thing for society. It is a public institution and as such it is the recognition that society has a stake in the family unit. If society benefits from the family (which it undoubtedly does) the family should benefit from society.

Seen negatively, if a family breaks down, the strain on society can be felt in a fiscally tangible way. A conservative estimate of the cost of marital breakdown, in a study commissioned by the Government in 1999, estimated the public cost of separation at £5 billion each year (Moving Forward Together: A Proposal Strategy for Marriage and Relationship Support for 2002 and Beyond, Lord Chancellor’s Department, April 2002) Let’s not be naïve: this cost would not diminish simply because of tax policies. But part of this cost to society could be alleviated by prevention, lessening poorer family’s financial burdens.

Equally, seen positively, there is ample evidence that the family provides the most secure and enduring setting for a child to grow up into a contributing, creative individual in society. Furthermore, a lifelong partnership provides comfort, companionship and care in old age, and is associated with a generally healthier lifestyle. These contributions should be recognized and encouraged, not branded as moralistic.

Christian assumptions underlying the wisdom of supporting the family are based in a reasonable faith. But for those who don’t share that faith, there is other evidence that helping families is good for society. If Christian assumptions produce an unpalatable obstacle to sceptics, the obstacle should be overcome by trusting the evidence rather than what they claim, in Defoe’s words, is astrology, prophecy or Lucifer’s illusion.

Lauri Moyle is Fellow of the Institute for Faith and Culture and works for the charity CARE