Back in the late 1980s when The Sun newspaper was famous for its outrageous headlines such as the notorious 'Freddie Starr ate my hamster,' the students at Wycliffe Hall, the evangelical Anglican theological college in Oxford, held a competition to see who could produce the best spoof Sun headline. The winning entry in the competition was the headline 'Sex change bishop in mercy dash to palace'. The reason this headline won was because it referred to topics frequently covered by The Sun (sex and the monarchy), it contained the promise of an exciting story ('mercy dash to palace'), and the reference to a 'sex change bishop' contained the necessary degree of outrageousness because the idea of a Church of England bishop having undergone a sex change was at that time completely ludicrous.

The way things have changed in both British society and the Church of England is indicated by the fact that the headline 'Sex change bishop in mercy dash to palace' is no longer at all implausible, apart from the fact that it would read 'Transgender (or 'trans') bishop in mercy dash to palace', the term 'transgender' (and its abbreviation 'trans') having replaced the term 'sex change'.

The Church of England now has a transgender archdeacon in the person of Rachel Mann, the Archdeacon of Bolton and Salford, who is a male-to-female transsexual, and given that bishops are frequently chosen from the ranks of the archdeacons, the fact that there is a transgender archdeacon suggests that there could also be a transgender bishop in due course.

Furthermore, the fact that there are now people who identify as transgender in many spheres of British public life means that the idea that the Church of England could appoint a transgender bishop who could perform a mercy dash to Buckingham Palace no longer seems particularly odd.

In the case of society in general, the prevailing view is that it should be up to each individual to decide which sex they want to identify with and, furthermore, the question of identity is seen as having been decided by the Gender Recognition Act which makes someone who obtains a gender recognition certificate a legal member of their chosen sex. In the case of the Church of England, the prevailing view has become that the Christian virtue of compassion means that each individual should be accepted as they are, and that this means affirming their identity as a member of their chosen sex.

Nevertheless, from a traditional Christian point of view there are still two basic reasons why it is problematic to accept someone as a member of their chosen sex if they are biologically a member of the opposite sex.

The first reason is that the two books of Scripture and nature which are the basis for our understanding of the activity of God both tell us that biology determines the difference between men and women.

In the case of Scripture, the Book of Genesis tells us:

' So God created man in his own image, in the image of God he created him; male and female he created them. And God blessed them, and God said to them, 'Be fruitful and multiply, and fill the earth and subdue it; and have dominion over the fish of the sea and over the birds of the air and over every living thing that moves upon the earth' (Genesis 1:26-28).

Here the state of being male and female is directly linked to the ability to reproduce, 'to be fruitful and multiply'. It is because God has given male and female human beings the necessary biological characteristics to reproduce that from Genesis 4:1 onwards human beings have children. Furthermore, from Genesis 4:1 the reproductive pattern determined by these characteristics remains unchanged throughout Scripture. It is men who beget, but it is women who conceive, carry babies in their womb, and then give birth.

What Genesis tells us is confirmed by the empirical observation of the human creatures that God has made. As the American writer Chrisopher Tollefsen observes:

"... our identity as animal organisms is the foundation of our existence as selves. But fundamental to our existence as this animal is our sex. We are male or female organisms in virtue of having a root capacity for reproductive function, even when that capacity is immature or damaged. In human beings, as is the case with many other organisms, that function is one to be performed jointly with another human being; unlike the digestive function, no individual human being suffices for its performance.

"Accordingly, reproductive function in human beings is distributed across the two sexes, which are identified by their having the root capacity for one or the other of the two general structural and behavioural patterns involved in human reproduction. In male humans, this capacity is constituted by the structures necessary for the production of male gametes and the performance of the male sex act, insemination. In females, the capacity is constituted by the structures necessary for the production of oocytes and the performance of the female sex act, the reception of semen in a manner disposed to conception."

There are various other physical and psychological differences between men and women, but they are all characteristics of human beings who are fundamentally differentiated by the fact that their bodies are ordered towards the performance of different roles in sexual reproduction and in the nurture of children once they have been born.

These differences that mean some human beings are male and others female have their origin at the moment of conception, and are ineradicable. Even though a person may take hormones and undergo surgery to block the development of, or to change, some of their sexual characteristics they nevertheless remain a person who is either male or female for the reasons just described.

The second reason why gender transition (trying to be a female if biologically male and vice versa) is problematic is because it involves violating the biblical teaching that we should live as the members of the sex that God has given to us. This teaching can be found in Deuteronomy 22:5 which prohibited cross-dressing on the grounds that to dress after the manner of the opposite sex was to infringe the normal order of creation which divides humanity into male and female.

It can also be found in 1 Corinthians 11:2-16 where Paul tells the Corinthians that men should follow the dress and hair codes which proclaim them to be male, and women those which proclaim them to be female because, to quote the Anglican biblical scholar Tom Wright, "God's creation needs humans to be fully, gloriously and truly human, which means fully and truly male and female."

This does not mean that Christians should uncritically embrace the gender stereotypes of any given society. What it does mean is that they should live in a way that proclaims to that society the truth of their creation by God as male or female.

As the Anglican ethicist Oliver O'Donovan has written in Begotten or Made?, the basic principle is that:

"The sex into which we have been born ... is given to us to be welcomed as the gift of God. The task of psychological maturity—for it is a moral task, and not merely an event which may or may not transpire—involves accepting this gift and learning to love it, even though we may have to acknowledge that it does not come to us without problems. Our task is to discern the possibilities for personal relationship which are given to us with this biological sex, and to seek to develop them in accordance with our individual vocations. Those for whom this task has been comparatively unproblematic (though I suppose that no human being alive has been without some sexual problems) are in no position to pronounce any judgement on those for whom accepting their sex has been so difficult that they have fled from it into denial. Nevertheless, we cannot and must not conceive of physical sexuality as a mere raw material with which we can construct a form of psychosexual self-expression which is determined only by the free impulse of our spirits. Responsibility in sexual development implies a responsibility to nature—to the ordered good of the bodily form which we have been given."

The fact that human beings are called by God to live out the sex given to them by God means that from a Christian perspective deciding to identify as a member of the opposite sex is not just an attempt to achieve something that is impossible to achieve - becoming a member of the opposite sex - but it is also something that is morally wrong. It is a sin.

As CS Lewis writes in his book The Great Divorce, there is an inescapable binary choice facing all human beings. 'There are only two kinds of people in the end: those who say to God, 'Thy will be done,' and those to whom God says, in the end, 'Thy will be done.''

Lewis' point is that God has given human beings freedom to shape their own destinies. We can choose to say to God 'thy will be done' and be happy with God forever in the world to come, or we can choose to turn our back on God. If we do this God will respect our decision, but the inevitable consequence will be that in the world to come we will be cut off from God and all good forever.

The fundamental problem with gender transition is that it involves a rejection, in both theory and practice, of the sexual identity which we have been given by God and thus a failure to say to God 'thy will be done.' It means a sinful refusal to either accept or live in accordance with the male or female sexual identity that God has bestowed upon us.

It might be argued that those who desire to engage in gender transition are not morally culpable because they genuinely feel that they are a member of the opposite sex. This may be true but the argument ignores the fact that they have a distorted view of their situation which they then make the basis of sinful actions. This is not in fact something which makes them unique. This is because, as a result of the Fall, human beings in general have lost the ability to always see things as they truly are (see Romans 1:21). Acts of sin (of whatever kind) occur when a distorted view of reality resulting from the Fall leads to wrong desires, which in turn give birth to wrong actions. Gender transition is just one form of this pattern.

All this being the case, how should Christians respond to those who have undergone gender transition or who are wanting to do so?

The answer is simple in principle, however difficult to put into practice. Christians need to practise a love which goes beyond simple affirmation.

As people of love, who value the God-given dignity of people who claim to be transgender as those whom God has created and for whom Christ died, we should be proactive in ensuring that they are not subject to harassment or violence.

As people of love, who recognize and value as a work of God the sex into which trans-identifying people were born, we should encourage them not to go down the path of gender transition. If they have gone down this path, love means helping them to accept and live out their original, God-given, sexual identity, while acknowledging the acute challenges doing this will raise, particularly for those who have undergone gender-assignment surgery or formed families in their assumed identity.

Martin Davie is a lay Anglican theologian and Associate Tutor in Doctrine at Wycliffe Hall, Oxford.