Is discipline a necesary feature of a true Church?

In the period immediately prior to the Reformation it was fairly obvious that the church could be defined as an institution with the Pope as its head. By carefully ignoring the schismatics of the East and putting down dissent, the Church could plod along with this neat definition. However, for the churches that emerged from the Reformation there was a need to attempt a redefinition along biblical lines. This was prompted not only by failure of the Roman Church but also by the many heretical bodies that sprang up in the wake of the Reformation.

Most theologians agreed in the distinction between the visible and the invisible Church, recognising from the Scriptures that until the day of judgment there will always be wheat and tares in the field. Beyond this point there were significant differences not so much about what is desirable in a true Church as about what is essential.

Some took the view that the only essential mark of a true Church is the preaching of the pure gospel of Jesus Christ. Beza is sometimes cited as an advocate of this 'single mark' view. Others added to this a second mark, namely the right administration of the sacraments of baptism and the
Lord's Supper. This, it would appear, was the line taken by Calvin. Of course those who held to just one mark were not against the sacraments, rather they recognised them as good but not essential to the being of the
Church. Still others took the view that there is a third essential mark of a true church, the exercise of ecclesiastical discipline. Peter Martyr is sometimes cited as an example of these.

The fine line between these distinctions can be illustrated by the two-mark Calvin, writing in his Institutes, book IV xii 4:

Those who think that the church can stand for long without this bond of discipline are mistaken; unless by chance we can afford to omit that support which the Lord foresaw would be necessary for us.

Calvin therefore clearly sees the necessity of discipline for the well-being of the Church but apparently was
reluctant to make it part of the essence of the Church.

What is the Anglican position?

Article XIX of the Thirty-Nine Articles mentions both preaching the pure word and the sacraments as defining a true Church but does not mention discipline.  However, it is clear from other Articles that discipline is to be carried out.  This is made explicit in The 'Homily Concerning the Coming Down of the Holy Ghost and the Manifold Gifts of the Same':

The true church . . . hath always three notes or  marks, whereby it is known: Pure and sound doctrine; The sacraments ministered according to Christ's holy institution; And the right use of ecclesiastical discipline. This description of the church is agreeable both to the Scriptures of God, and also to the doctrine of the ancient Fathers; so that none may justly find fault
therewith.

Since the Homilies in some sense interpret the Thirty Nine Articles the Church of England therefore takes the view, in theory at least, that discipline is essential for a true Church.

See Also

Article 33 - The excommunicated: how they are to be avoided

Clergy Discipline - under Ministry

Articles relevant to this issue

How Many Marks  - Cross†Way article

Discipline in the Local Church - how discipline should be administered in the local church. Cross†Way article.

The Word and Discipline in the Church. Churchman article (1989) by Hugh Craig.