Provinces signing the Anglican Covenant will be agreeing that:
We, as Churches of the Anglican Communion, under the Lordship of Jesus Christ, solemnly covenant together in these following affirmations and commitments (Preamble)
In adopting the Covenant for itself, each Church recognises in the preceding sections a statement of faith, mission and interdependence of life which is consistent with its own life and with the doctrine and practice of the Christian faith as it has received them. It recognises these elements as foundational for the life of the Anglican Communion and therefore for the relationships among the covenanting Churches (§4.1.2).
Its proponents believe the 'bonds of affection which hold us together' (Introduction §5) have been judged and found broken. Once it is signed, all current and future member churches will be bound together by their assent to the Covenant's statement of faith and order. (Precisely what 'consistent' means in this context will be worked out in practice in the years to come.)
This would be to turn Anglicanism into a confessional denomination. Until now Anglicanism has usually allowed diversity of opinion on controversial issues, in the belief that we learn from each other in open dialogue and from our own and other people's experiences. Where there is genuine disagreement, therefore, it should be possible for all sides to debate the issues openly until consensus is reached. This is central to the theology of classic Anglicanism.
At the opposite extreme is a tradition which developed out of Puritanism. Many Reformation Puritans believed that the proper Christian response to any question is to look for the answer in the Bible. Once found, this 'biblical answer' is declared the only legitimate one for Christians. Churches based on this principle expect to have an official line on every contentious topic, and expect those with teaching authority to defend it. Those who dissent are considered 'unbiblical' or 'unsound'.
Thus the Puritan tradition sees disagreement as a threat to unity and is more inclined to expel dissidents. This is why they accuse liberals of trying to impose a revisionist agenda on the Church. It is this tradition which lies behind the claim - which astonishes most Anglicans - that one gay bishop, anywhere in the world, generates a crisis for the whole Anglican Communion.
Many Covenant supporters deny that they want a confessional church. This may be for a number of reasons. Some do want a confessional church, but are anxious to downplay the implications of the Covenant until Provinces have signed it. Others support the Covenant because they would like to tie up some loose ends in church law, or because they think a confessional church is a price worth paying to avoid schism. Others again have, without realising it, learned to accept the increasingly authoritarian mood.
Moreover the distinction between the two allows for fuzzy edges. Most church leaders have taught that there are some beliefs which all Anglicans should accept. If we ask what they are, with the exception of the Thirty-nine Articles Anglicans have been content with general affirmations of the Bible and the Creeds rather than listing precise doctrines. For example, throughout the sixteenth and seventeenth centuries there was much emphasis on the principle that the Bible contains all things necessary to salvation, but nobody produced a list of what those things were. Recently there has been debate about whether or not same-sex partnerships are adiaphora, matters on which Christians can agree to disagree.
In practice this fuzziness has proved most valuable, allowing the core texts to be interpreted in different ways on different occasions. William Abraham's recent book Canon and Criterion in Christian Theology argues that there are two distinct concepts, which Christians have identified for so long that we rarely realise the difference. A canon is but a list: the canon of the Bible was first established as the list of books to be read in worship. Later, well after it had been established, it came to be interpreted as a criterion: that is, as a way of establishing the limits of acceptable Christian belief. It is possible for Christians to value its central documents as canon, without treating them as criteria to answer every question.
Those who prefer a confessional church demand more clarity. Some of the more conservative leaders in the Anglican Communion are used to treating Anglicanism as a confessional denomination, and are therefore frustrated that they had no means to sanction the church of the USA, nor to expel it, nor even to dissociate themselves formally from it. This seemed to them a significant weakness in global Anglicanism and they look to the Covenant to provide the remedy.