The primary service which Systematic Theology performs for the preacher is to provide him with his message. But that's not all. It should also give his message biblical proportion and balance. After all, it is only too easy to ride hobby-horses, as witness the story of the old Presbyterian minister whose sermons invariably had the simple headings, 'First, a word about the text. Secondly, a word of application. Thirdly, a word about infant baptism.'

The idea of a 'hierarchy of truths' has become commonplace since it was endorsed by Vatican II, which laid down that Catholic theologians engaged in ecumenical dialogue with 'separated brethren' 'should remember that in Catholic doctrine there exists an order or "hierarchy" of truths, since they vary in their relation to the foundation of Christian truth' (The Decree on Ecumenism, Chapter I.11). But the idea is as old as St. Paul's reminder to the Corinthians that he had passed on to them 'as of first importance' that Christ died for our sins, was buried and was raised on the third day' (1 Cor. 15:3,4). Calvin laid hold of it boldly: 'For not all the articles of true doctrine,' he wrote, 'are of the same sort.  Some are so necessary to know that they should be certain and unquestioned by all men as the proper principles of religion ... Among the churches there are other articles of doctrine disputed which still do not break the unity of faith.' (Institutes IV.I, 12).

This does not mean that anything revealed in Scripture is unimportant, or that we should keep silent on any doctrine for which we think there is good biblical evidence. But it does mean that all doctrines are not to have the same prominence in our message. Some are fundamental in a way that others are not, and one of the functions of Systematic Theology is to highlight the proportions of truth. Certain doctrines are referred to in Scripture far more frequently than others; they are found in every era and every genre of revelation; and in some instances they are even declared by Scripture itself to be fundamental. For example, the Apostle John lays down that to deny that Christ is 'come in the flesh' is to reflect the spirit of antichrist (1 Jn. 4.2); Paul anathematises those who preach justification by works (Gal. 1.8) and tells the Corinthians that without the physical resurrection of Christ our faith is vain (1 Cor.15.17); and in his conversation with Nicodemus Jesus himself underlined the paramount importance of the new birth (Jn. 3.3).

Precisely because of the clarity with which such doctrines are revealed, they form a core of beliefs shared by Christians everywhere. This was encapsulated in the so-called Vincentian Canon laid down by Vincent of Lerins in the 5th century: Catholic truth, as distinguished from heresy, was what had been believed 'always, everywhere and by everybody' (quod semper, quod ubique, quod ab omnibus).  

It was this unanimity that led to the formation of the 'dogmas' of the church, taking the word 'dogma' in the specific sense of doctrines which have received formal ecclesiastical sanction, often with the view of distinguishing them from the views of heretics. Prominent among these would be the decrees of the great Ecumenical Councils, especially those of Nicea, Constantinople and Chalcedon, which expressed the Christian consensus on the doctrines of the trinity and the incarnation; and the Council of Ephesus (431), which formally condemned Pelagianism. 

The preacher will seldom find it necessary to quote these councils, but the elements of their doctrines (for example, the deity of Christ and the depravity of man) will outcrop regularly in his sermons, and undergird all his worship. At the Reformation these dogmas were reaffirmed by both Romanism and Protestantism. Lutheranism proclaimed its core doctrines in the Augsburg Confession (1530) and the Formula of Concord (1576). The Reformed Churches proclaimed theirs in such statements as the Second Helvetic Confession, the Heidelberg Catechism and the Westminster Confession.

When quarters of later Puritanism, obsessed with the idea of sola scriptura, rejected the whole idea of man-made creeds and adopted a policy of non-subscription, it set out on a fatal journey towards Unitarianism. Where, by contrast, subscription is taken seriously, creeds and confessions serve to identify the doctrines on which all are agreed and which no pulpit will contradict.  

Even among creeds and confessions, of course, there is a hierarchy. The articles of the Apostles' Creed, for example, demand a greater prominence than the distinctive doctrines of the Synod of Dort. But this does not affect the central principle: the 'dogmas' of the church demand greater prominence than the individual preacher's personal beliefs.

It is not simply a matter, however, of the clarity with which certain beliefs are revealed or the unanimity with which they have been received. There is a further consideration. Precisely because it is systematic, Systematic Theology knows that certain articles are key-stone doctrines. Once they are removed, the whole arch falls.  This is what Luther meant when he declared, 'If the article of justification is lost, the whole of Christian doctrine is lost'.[1] Even more fatal would be the loss of the doctrines which underlie justification itself (the incarnation and the atonement). If we lose the deity of Christ, our worship becomes idolatry; and if we lose the doctrine of creation we have no God at all since the minimal definition of god-ness is that he is the Maker of heaven and earth. Lose any of these and the church loses her foundation. This was the whole point of the original Fundamentalist debate 100 years ago, regardless of how 'fundamentalism' came to be seen later. The very concept of 'fundamentals' rested on the notion of a hierarchy of truths. The fundamentals were the foundation: remove them, and the whole edifice of Christianity would collapse.

The Westminster Confession introduces, albeit incidentally, another criterion to guide us as we reflect on the hierarchy of truths. It speaks of certain doctrines as 'necessary to be known, believed and observed for salvation' (1:7); and it goes on to declare that these are so clearly propounded and opened in Scripture that 'not only the learned, but the unlearned, in a due use of the ordinary means, may attain unto a sufficient understanding of them.' (italics mine). The reference to 'a due use of the ordinary means' is not pointing primarily to Bible  study-aids such as commentaries and dictionaries (to which few of the 'unlearned would have had access in the 17th century).  It is pointing to the preaching of the word, and assuming that the main function of preaching is to propound and open these essential doctrines.  This same point was made in the Westminster Shorter Catechism when it declared (Answer 89) that, 'The Spirit of God maketh the reading, but especially the preaching of the word, an effectual means of convincing and converting sinners' (italics mine).

The underlying principle here is stated by Augustine in his Confessions (I:1): 'who calls upon you when he does not know you?'  There clearly are certain doctrines without which Christian faith and prayer are impossible, and such doctrines must stand at the very top of any hierarchy of truths. We might say, for example, that the minimum would be what would sustain the faith of a child.  But then, when we come to Christ we are all spiritual children; and even in the case of children it would be arbitrary to limit her faith to what she can articulate in words. 

Yet we can safely say that the beliefs of the spiritually re-born would not have to include premillennialism, particular redemption or divine impassibility; nor would many of us want to follow the so-called Athanasian Creed in pronouncing an anathema on those who do not believe (or know) that, 'in this trinity none is afore, or after another; none is greater, or less than another; but the whole three Persons are co-eternal together: and co-equal.  So that in all things, as aforesaid, the Unity in Trinity, and the Trinity in Unity is to be worshipped.'  If we limit church-membership to those who can intelligently affirm such a creed, we shall soon empty our churches.

The question is, What level of knowledge is necessary to sustain the primary Christian graces of faith, hope and love?  If we are justified by faith, we must have some understanding of justification; if we are to live in hope we need to believe in the resurrection of Christ and in the promise of eternal life; and if we are to love the Lord we need to understand the wonder of his self-sacrifice on the cross of Calvary.

Recondite though it seems, then, the concept of a hierarchy of truths has distinct practical implications.

First, it has a bearing on admission to membership of the church.  The apostles baptised only those who gladly received the word (Acts 2.41), and every church needs to have some such criterion, even while remaining painfully aware that ministers and elders can judge only the outward appearance.  The secrets of the heart are beyond human scrutiny, and the idea of a pure church an impossible dream.  Besides, we must always remember that the ability to describe our faith in words varies enormously from believer to believer.  Yet any credible profession must embrace a knowledge of the Name into which we are baptised, and that Name includes both who he is and what he has done for our salvation.

Secondly, the concept of a hierarchy of truths has a clear bearing on the question of admission to office, and particularly to the ministry of the word. This takes us to a higher level than what is required for admission to ordinary church-membership.  The elder must not only be mature and blameless: he must be 'apt to teach' (didaktikos); and in any Confessional church he must be in a position where he can sincerely and intelligently subscribe to the church's creed. That creed should include all fundamental doctrines but, equally, it should include only fundamental doctrines. 

The problem we run into here is that denominations will wish to safeguard their own distinctive doctrines, which are, after all, the reason for their separate existence. Unfortunately, these distinctives are seldom fundamental in any real theological sense.  Believers' baptism is not a fundamental Christian doctrine, but it has to be included in the basis of faith of any Baptist church; and the church has a right to be assured that the pastor holds to it sincerely and intelligently. Similarly, knowledge of the leading principles of Presbyterianism is hardly a condition of salvation; yet they have to form part of the Basis of Faith of any Presbyterian denomination. Sad though it may sound, no church can in practice be simultaneously Presbyterian, Episcopalian and Congregational; or Baptist and Paedo-Baptist.

Thirdly, the idea of a hierarchy of truths is of crucial importance in ecumenical ecumenical relations. If unity is to be unity-in-the-truth there has to be agreement as to what the truth is. But there also has to be agreement on the relative importance of areas of disagreement. In theory, there should be room in every true church for John Owen, John Wesley and Charles Spurgeon. They were agreed on all the doctrines of the early creeds and on all the great watch-words of the Reformation. But they were not agreed on such doctrines as predestination, the extent of redemption and the nature of sanctification. The question is (and Systematic Theology by itself cannot answer this) whether such disagreements are sufficiently serious to require their separate existence, worshipping side by side under independent jurisdictions.

How, in other words, do we adjust the competing claims of Christian unity on the one hand, and freedom of conscience on the other?

Donald Macleod is Professor of Systematic Theology at the Free Church of Scotland College, Edinburgh, Scotland. He is the author of A Faith To Live By (Christian Focus, 1998), The Person of Christ (IVP, 1998) and Christ Crucified (IVP, 2014)

[1] Martin Luther, Lectures on Galatians 1535, ed. Jaroslav Pelikan (Luther's Works, vol. 26. Saint Louis: Concordia Publishing House, 1963), p. 9