Proponents of the Anglican Covenant argue that we need it because the Anglican Communion accepts that same-sex partnerships are immoral, and it therefore needs to distance itself from the churches of the USA and Canada which have formally rejected this teaching. But is this a valid argument?

Not as far as the actual Anglican situation and biblical texts are concerned. Another question is whether the immorality of same-sex partnerships is essential to Christian belief or a question on which we can agree to differ. The current debate often uses the Greek word adiaphora, 'indifferent things'.

It is generally agreed that throughout most of Christian history most church leaders have considered same-sex partnerships immoral. However the same can be said about a great many other things, like lending money at interest, which we today no longer consider immoral. In practice Christians have believed different things at different times.

So is there a way of distinguishing between the teachings we ought to accept in order to count as Christians, and the things on which we can agree to differ? If so, is there a longer list of things to accept in order to count as an Anglican?

In the current debate there has been much discussion of these questions. Two supporters of the Covenant are N T Wright and Andrew Goddard. Wright's Presidential Address of May 2010 discusses it at some length.  He accepts the distinction between essentials and adiaphora (things on which we may agree to differ) but argues that 'the question of whether a particular issue is adiaphora or not cannot itself be adiaphora'. From this he concludes that an international authority is needed to determine which issue comes under each heading. [A Modern Church response]

Goddard argues (in Chapman, Ed, The Anglican Covenant, Mowbray, 2008, pp. 56-57) against the view

that because Anglicanism has always been diverse and/or that it is inherently inclusive, it therefore follows that what has happened in North America cannot be judged wrong or un-Anglican. It therefore should not significantly alter relationships and structures within the Communion.

This is a good summary of the characteristic liberal approach. Goddard replies

My problem with this position is in part that it does not seem to make Scripture the authority against which our diversity must be weighed and tested. But it is also that it misses the key point at issue and lacks coherence as a response. It would appear to have to choose between two concrete outworkings of its emphasis on diversity. Either this view  refuses to set any limits at all to Anglican (or indeed Christian) identity, seeing diversity as infinitely elastic with no impact on Anglicanism's coherence or its unity. This is, in reality, a view that few if any really accept. Or its vision and principle of diversity is one which is selectively applied. It is used to justify 'acceptable' diversity (e.g. clergy in same-sex unions but not laity presiding at the Eucharist, or vice versa) but the fundamental question of how we discern as a Communion what is legitimate and what is illegitimate development is then left unanswered.

In these texts both Wright and Goddard accept a distinction between essentials  and adiaphora and look for an authority to establish it. Wright proposes  an international authority, a kind of Anglican pope (though not necessarily a single person). Goddard does two things. First he appeals to Scripture as the authority, but without offering any interpretative principles to justify such an emphasis on same-sex partnerships while ignoring the many hundreds of texts forbidding practices which are common today. This is a very frequent complaint by liberals about conservative evangelicals: they condemn some but by no means all of the actions  forbidden in the Bible, and do not provide a satisfactory principle of selection. [Puritans, sectarianism and the Bible]

Secondly, Goddard argues that the liberal position lacks a principle for distinguishing between essentials and adiaphora.  The problem here is that although he is absolutely right about this lack, he lacks it too. Appealing to Scripture's authority does not in fact produce any such principle, and even if he plumps for Wright's international authority he is only giving the problem to somebody else, not solving it.

So is there any principle at all to distinguish between the essentials of faith and adiaphora? This issue is as old as Protestantism: in the sixteenth century Richard Hooker argued against the Puritans about it. If we ask how, in practice, Christians have handled this question between then and now, we will not find any one principle dominating. Before the nineteenth century slavery debate, for example, nobody would have foreseen that such a large number of biblical texts, taking slavery for granted as part of society, would have been put to one side as a new moral norm emerged to became standard Christian belief. In practice each debate hears a range of voices, some appealing to biblical texts, some to contemporary experience, some to moral principles, some to what has been done before. This is what liberals would expect: different considerations each play their part in contributing to understanding. In this sense Hooker's 'three-legged stool' of scripture, reason and tradition summarises well how we handle most of our controversies: we have a range of considerations, none of them infallible, so the more the better. The history of church disputes and their resolutions provides no confidence that a predetermined conflict-resolving principle would have helped.

Wright and Goddard both want a predetermined system for resolving disagreements in the church. Furthermore they both want it to be a church system, something which owes nothing to the ordinary world outside Christian doctrines. There is no such system. The church is part of the world. Christian opinion on slavery changed because of stories about what it was like to be a slave, not because of biblical texts. After decades of disapproval Anglicans eventually decided that contraception was morally acceptable, not because of biblical texts or church dogma but because of their experiences of intimacy, experiences they shared with their non-Christian neighbours. The ethics of same-sex partnerships will eventually be resolved in the same way.

History therefore indicates that we should not expect to find a permanent principle for distinguishing between essentials and adiaphora.  Henry McAdoo puts it well when he declares (The Spirit of Anglicanism, p. 1) that Anglicans do not believe anything because it is Anglican, but only because they think it is true. Similarly, in all other fields of research it is recognised that the search for truth will fail if there are statements of fact which researchers are forbidden to challenge. If some things are considered so unquestionably true as to be off limits, three things go wrong. Firstly they may not be true in all circumstances, so the limits of their reliability need to be checked. Secondly, if the truth of them is closely examined it may lead to other truths. Thirdly, if we stop asking why something is true we shall forget what it means.

Which teachings are essential, and which are adiaphora, change over time. The changes are slow, but real. Even the doctrine of the Trinity took centuries to be established. What Christians believe today is nothing like what our predecessors believed in the Middle Ages. The distinction between them is not as hard and fast as the current generation of 'conservatives' would like.

This is a good thing: it means we are not trapped in our past. God permits us to ask new questions.