The sheep baa-ed and bleated with pleasure. Then, as the shepherd threw away his crook and began to divest himself of his shepherd's garments, they gasped in horror. The Head Shepherd was none other than their old enemy the wolf. They had been warned to beware of a wolf in sheep's clothing but they had never been warned to beware of wolves disguised in a shepherd's mitre and crosier.

Last week, Justin Welby, Archbishop of Canterbury told the Mothers' Union that the idea of a Victorian golden age of traditional family values was a "myth." The "myth" of stable Victorian values was "just that--mythology." At the 140th anniversary of the Mothers' Union, the spiritual leader of 85 million Anglicans told an international gathering of women that they had to face up to modern day society where divorce and same-sex couples are the norm.

When the shepherd speaks well of the wolf, the sheep are in serious trouble. What do the sheep need to know to debunk Welby's fatally flawed sermon?

Welby fails to distinguish between facts and values. No one makes this distinction more succinctly than former President of the British Academy and secular philosopher, Sir Anthony Kenny: 'In order to judge Victorian values, the question each of us should ask ourselves is not would I like to be the kind of person the Victorians were; but would I like to be the kind of person the Victorians admired. In my case, the answer to the first question would be a definite no, the answer to the second question would be a qualified yes.'

Welby could well have been urging the Mothers' Union to abandon the biblical myth of the traditional family since there is no perfect family in the Bible. Even Jesus's father suddenly disappears in the middle of the story! Most families in the Bible are dysfunctional--as Welby admits his family also was when he was growing up. But is there a family value to which both Jews and Christians aspire in spite of the social pressures of the cultures around them? Jews and Christians believe that this norm is to be found in the creation story in Genesis 2 with its ideal of a man leaving his father and his mother and cleaving to his wife and the two becoming one flesh. For Christians, this becomes normative because it is reiterated by the Lord Jesus Christ in the gospels of Mark and Matthew.

The image of the Victorian family--husband, wife and children--gathered around the hearth was meant to represent an ideal to which the Victorians aspired. For John Ruskin, the role of the wife and mother was central, for "where a true wife comes, this home is always around her." Ruskin's understanding of the Victorian wife is similar to the role of the wife in Proverbs 31--a "myth"--if one understands the term "myth" as an idealised conception of a person or thing to which we aspire and which is the foundational narrative of society's norms.

Yet, Victorian literature does not shy away from exploring the tension between representation and reality. Charles Dickens, Elisabeth Gaskell, and the Brontë sisters, in particular, focus on the ways in which the middle-class family could be troubled or unhappy or broken. After all, we live in a fallen world, and the world's first family in the Bible is also the family where the world's first fratricide takes place--Cain murders his brother Abel.

I have been a minister for over 25 years. One of my greatest joys and privileges has been to solemnise weddings. Many of the weddings I conducted were during my time as Chaplain to the Old Royal Naval College, Greenwich. The Chapel is a stunning architectural gem designed by Christopher Wren. Before I could solemnise the wedding, I would ask every couple to attend services for at least six to nine months and do a five-session marriage preparation course which I organised from home.

During the wedding service, I would preach my sermon to a packed congregation of family and friends. I always warned the bride and groom that I was going to say something radical and politically incorrect about marriage and family. Would they mind? I would, of course, be quoting Sir Jonathan Sacks who was Chief Rabbi at that time: 'Today, we have divorced sex from love; love from commitment; commitment from marriage; marriage from having children; and having children from bearing responsibility for nurturing them and bringing them up. It is as if somebody had planted a bomb in the very midst of our most sacred institution and all we have left is fragments. All the bits are there, but they are no longer connected. We have lost--or we are losing--that one institution that brought together sex and love and companionship and trust and stability and fidelity, and bringing new life into the world and caring for it in its dependent years.'

I was well aware that for most of the congregation the facts and sometimes even the values were very different in a postmodern world--divorce, broken families, children born out of wedlock, cohabitation, and same-sex partnerships. But here were two people who had fallen in love with each other and fallen in love with an ideal. They would pledge to live together 'from this day forward; for better, for worse, for richer, for poorer, in sickness and in health, to love and to cherish, till death us do part; according to God's holy law.'

They expected me to uphold this ideal and as their shepherd, it was my solemn duty to warn them of the ideological wolf that was prowling around their sheep pen. Were I to have done otherwise, I would have been no shepherd at all, but a hireling--or even worse, a wolf in sheep's clothing.

The Rev'd Dr Jules Gomes is pastor of St Augustine's Church, Douglas, on the Isle of Man.