Quadrilateral means four-sided or having four parts. In Anglican history it is usually applied to a Statement first approved by the Protestant Episcopal Church at Chicago in 1886 and then approved by the Lambeth Conference in slightly amended form in 1888.
At this time in the late 19th century, in the history of the Church of England and her sister Provinces overseas, there was a general sense of security in the commitment to the Anglican Way and to its historic Formularies (The Book of Common Prayer, the Articles of Religion & the Ordinal - Ordination Services). From this solid base, and in part because of the impact of the great missionary movement of the 19th Century, leadership of the Protestant Episcopal Church in particular was considering seriously the call of God the Father & our Lord Jesus Christ to unity of the various denominations or jurisdictions of the one, holy, catholic and apostolic Church.
In the four-sided Statement, known as the Quadrilateral, the American Church, followed later by the whole Anglican Communion of Churches, stated that "the four Articles supply a basis on which approach may be by God's blessing made towards Home Reunion." The four are the Scriptures, the two Creeds, the two Sacraments and the historic Episcopate.
We need to be perfectly clear that the Quadrilateral is not and was never set forth to be an internal confession of faith for Anglicans or Episcopalians. Such an internal confession already existed in the Formularies, based upon Holy Scripture.
Thus it is a serious mistake for modern groups to use the Quadrilateral as if it were a confession of faith for Anglican churches, societies or organizations. If the Anglican Faith is now reduced in 2003 to that which was in 1888 regarded as the minimum basis for negotiations with other Christian bodies towards the possibility of inter-communion and unity, then we have certainly much reduced what it is that we believe, teach and confess as Anglican Christians.
In particular, there is removed from the basis of the Anglican Way that which has been its unique possession, as both a Formulary and an authoritative basis for worship since the reforms of the 16th century, the authentic Book of Common Prayer.
A further thought -- What the use of the Quadrilateral in ecumenical relations preserves is the important principle that reform and renewal in the life and history of the Church of God is achieved by looking backwards (to the authentic sources of the Faith) even as we simultaneously look up to the exalted Lord Christ for reviving grace. When the Church seeks to bring in change through innovation (introducing that which has never been there before - e.g. women's ordination and gay marriage ) then she is pursuing reformation not by looking backwards (in order to go forward in faith , hope and charity) but by looking forwards in optimism with the hope that what is introduced will work out as fine. And to cover this new principle of reformation forwards the ecumenical world, followed by the Anglican, invented a modern form of the old doctrine of reception (if it is of God it will be received, and, if it is not, then it will eventually be seen to be inappropriate or wrong).
Where the Quadrilateral is rightly used in ecumenical relations there is not the possibility of innovations belonging to the principle of reformation forwards, but there is the real possibility of moves towards cooperation and fellowship between long divided denominations and churches on a sound, historic and biblical basis.
Let us use the Quadrilateral aright and experience its wisdom in practical, ecclesial contacts.
The Rev'd Dr. Peter Toon M.A., D.Phil. (Oxon.)