Biblical Perspectives Magazine, Volume 25, Number 12 March 19 to March 25, 2023

The Benefit of Having a Worthy Opponent

How the Theology of Seventeenth-Century Puritans
Can Be Complemented by the Nineteenth-Century German Thought
Known as the Mercersburg Theology

By Rev. Joel Kletzing


Puritan Spirituality

Three Puritan works related to sanctification will serve as representatives of this movement which Nevin at times sharply criticized, although another paper in this series has demonstrated that a great deal of Mercersburg's disagreements with Puritanism was actually directed at the later New England version.

Keeping the Heart

John Flavel (1627-1691), minister of Dartmouth, England, wrote Keeping the Heart: How to Maintain Your Love for God, and in it, as J. I. Packer points out, he demonstrated that real Christianity consists of communion with God. 1 The alleged abstract decrees which failed to fit well into Nevin's union-based theology, were recognized by the Puritans as true because the Bible treated them as God's means of managing His universe. And they found in them the foundation of union and communion with God. In contrast to Nevin's philosophical, though often useful, grid through which He viewed the Scriptures, products of the Puritan era such as this work of Flavel's demonstrate a hunger and thirst for God's holy goodness which is not as easily absorbed through Mercersburg's dogma.

Rather than a desire to see the singular and particular reunited with the general, Puritans such as Richard Baxter, for instance, yearned for the fulfilment of the sure hope of being with Jesus in heaven. 2 Such longing fires discipleship with greater energy than debates about the generic life of the world.

Packer has distilled out of the whole of Puritan theology a definition of the heart. His insight is this:

the controlling source of all that we do in expression of what we are: all our thoughts, desires, discernments and decisions, our plans and purposes, our affections, attitudes and ambitions, all the wisdom and all the folly that mark our lives, come out of, and are fueled, serviced and driven by, our hearts, for better or for worse. 3

Salvation, of course, consists in receiving a new heart (Ezekiel 36:26-27). From that new heart comes faith in Christ as well as love to God and others. This theology is not technically different from Nevin's because his writings reflect allegiance to these same truths.

Dr. Packer assesses Flavel's work as aiming at godliness with peace and joy in the Lord. 4 After reading much of Nevin's writings, even with consideration of the differing contexts in which each of them ministered, one is left with the impression that Nevin focused on a logical and psychological explanation for conversion which noted delight in Christ as a byproduct, while Flavel aimed at delighting in God and used reasoning as necessary to understand the divine work of redemption and to construct a sturdy platform upon which to pursue godliness.

While Flavel did not take up a goal of vindicating autonomous human volition as Nevin did, the book under consideration here assumes personal responsibility, for it is written in the context of talking to oneself before the Lord, reminding self of truths of grace and praying for strength. He cautions against sin and Satan tempting the Christian to follow blind desire without thinking. Citing a summary from Packer once again, he comments that the heart must be kept steadily zealous for God's glory and consciously close to Christ, all the while being prepared for periods of intense struggle in order to stay on course. 5 In Flavel, the heart of a pastor shines brightly. Nevin, on the other hand, was not a pastor. In reading both schools of thought, one begins to wonder if the concrete results of Flavel's writing, which Nevin classified as belonging to a school of thought based on abstract decrees, may not promote sanctification more than the abstract conclusions produced by the insistence on a rigidly organic model of life in the universe which does incorporate the covenants, predestination (in some form), the atonement, etc., not as central streams carrying salvation forward but almost as props along the riverbank while the stream of organic life itself flows forward among them. Ironically, the organic does not seem as warmly connectional as the allegedly abstract which brings God near to His people through His Word. Nevin's work is not to be abandoned, for it adds depth of perspective on the glorious work of salvation (especially participation in the life of Christ) and of the mystery of union with God.

Flavel chose as a Scriptural base for his work Proverbs 4:23 – "Keep thy heart with all diligence; for out of it are the issues of life." Of the heart Flavel wrote that "the eye of God is, and the eyes of the Christian ought to be, principally fixed upon it." Further, he explained that "the greatest difficulty in conversion is to win the heart to God; and the greatest difficulty after conversion, is to keep the heart with God." 6

Flavel explains he is not proclaiming a gospel message that invites sinners to save themselves. Only God's power can truly keep a believer's heart, yet each bears the duty to seek Christ's power and victory over sin. 7 This is similar to Nevin's care to include both divine necessity and human action, but it differs from Nevin in that Flavel will push the cross into the forefront as the symbol of hope and full fruit of the incarnation.

Regeneration is presupposed before one begins to attempt to keep the heart. Regeneration is necessary to plant within the heart a "new spiritual inclination." 8 The unrenewed heart is fixated only on self. Originally, at creation, man was oriented toward God with no disorder in his heart. At that time he possessed complete knowledge of God's will, and his will complied. All appetites and powers were subordinate to this obedient will. The entrance of sin into the world corrupted the human heart to become disordered, self-dependent, self-loving and self-seeking. 9

Preserving the heart, then, is the constant and diligent care of a renewed person to preserve the soul in the gracious new state in which it has been placed. In order to do this, one must frequently analyze the condition of the heart. Deep humiliation must be demonstrated for the evil discovered in the heart. Next, one must plead with God for Him to purify what is discovered to be defiled and disordered. Guards must be set on practices and habits so as to deny opportunity for sin. Holy jealousy must be maintained over the heart, being intentional about living in the fear of the Lord. Finally, one must live conscious of God's presence daily. 10 "I never knew grace to thrive in a careless soul," he wrote. 11

If Nevin were to add anything to the list, it would likely be that this process is not to be carried on wholly subjectively, but subjectivity must be balanced with a healthy objectivity of the life of the church, including its liturgy and sacraments. He would be concerned to join substance and form, believing that the life of Christ in the individual could not be divorced from the life of Christ in the church.

Flavel, on the other hand, makes disparaging comments about formalists. 12 Certainly he rightly contends with those who embrace form without inner subjective substance, but not all who use forms are necessarily void of healthy subjectivity and real union with Christ. He well explains that God disdains outward obedience and sacrifice from those whose hearts are far from honoring Him. 13

A statement from Flavel which touches on organic relationships fails to bring clarity. He held that Christ is the originating root of a Christian, but also that grace is a root originated, planted and influenced by Christ. 14 It makes more sense that the believer is organically related to Christ and partakes of His life by grace rather than a person being organically bound to grace itself.

The gracious heart, kept diligently, will daily be nourished by precious thoughts of Christ. On the other hand, if heart maintenance is neglected, then even if one were to sit under the richest of teaching and participate in the ordinances of the church, there will in the end result no improvement. It would be as if there were a leak in the bottom of the soul. 15

Special times are identified when extra diligence is required in keeping the heart. Among these are times of prosperity when the heart may become proud and earthy. 16 God cherishes the rightness of the heart rather than outward financial success of an individual. Earthly things can clog the path of the soul bound for heaven. This work is saturated with Scriptural examples and practical insight as to how to act in each particular situation noted.

After prosperity, adversity appears on the list of special times when the heart must be kept, so that it does not turn in rebellion against God or fail in a faithful commitment to follow where He leads. 17 It may be that through outward losses God is humbling His child and actually preserving the soul from temptation or destruction. Flavel counsels, "Your own discontent is that which arms your troubles with a sting; you make your burden heavy by struggling under it." "Did you but lie quietly under the hand of God, your condition would be much more easy than it is." "God throws away some comfort which he saw would hurt you, and you will throw away your peace after it." 18

Another occasion to be vigilant is that of persecution. Flavel's insight is that "It is not our work to rule the world, but to submit to him that does." 19 The church's blessing must not be gauged in terms of outward prosperity. Persecution reveals the heart, causes one to excel in prayer and to long more for heaven. The author asks, "Is it well then to repine and droop, because your Father consults the advantage of your soul rather than the gratification of your humours? Because he will bring you to heaven by a nearer way than you are willing to go?" 20 Countless blessings belong to the Christian in spite of any trouble experienced on this earth. The blessings rooted in union with Christ cannot be ruined by evil on earth. "Shall light troubles make you forget weighty mercies?" 21 Nor can electing love be annulled by the pain of common providence. Flavel offered the comfort that "while prosperity and impunity slay the wicked, even slaying and adversity shall benefit and save the righteous." 22

While giving practical instruction about keeping the heart in times of great calamity or war, Flavel wisely warns that guilt softens the spirit and produces cowardice while "the righteous are as bold as a lion. 23 Recall how the guilty Herod was afraid John the Baptist was risen from the dead.

In guarding the heart during times of deprivation, it is helpful to remember that in history God subjected even the holiest of men to times of severe need. So such a state cannot be interpreted as hatred from God. Consider the value of God's sure promises. "It is better to be as low as hell with a promise, than to be in paradise without one." 24 There is a position worse than being denied earthly comforts; it is being denied a share in Christ along with its resulting peace and pardon. 25 The Christian should not be discouraged by running short of funds here, for upon the soon arrival in the Father's house, all will be supplied in abundance. 26

When injuries are sustained, the heart must be guarded against vengeful impulses. When carnal reason lobbies for hatred of an enemy, conscience should reply that God deserves to be obeyed. By vengeance a single enemy can be destroyed. By exercising self-control, the three enemies of lust, Satan and the enemy's wicked heart can all be defeated. 27

The heart must be counseled in times when Satan tempts, that if the temptation seems little and therefore the sin excusable, the subject has lost sight of the degree of Majesty in heaven that would be offended. There is no little hell for little sins. Flavel inquires, "Will you provoke God for a trifle? Will you destroy your peace, wound your conscience, and grieve the Spirit, all for nothing?" 28 It is dangerous to presume upon God's mercy as an excuse to proceed into sinning. There is no promise in Scripture for mercy to be extended to presumptuous sinners. 29

Without keeping the heart, Flavel maintained, all other duties performed by a Christian are of no value in Christ's estimation. True Christianity is not about only talking like a Christian (or even a theologian) or engaging in religious activity, but in keeping the heart. 30 Keeping the heart will yield lively communion with God, clear sight of Christ first in a sermon before others can recognize Him, the first seal from Christ in the sacrament before others, as well as first communication of grace and love in prayer. 31 In other words, the desire of Mercersburg to maintain a high, objective view of the church is nothing without a rich subjectivity at work in the form of individual heart maintenance.


  1. J. I. Packer, "Introduction," in Keeping the Heart: How to Maintain Your Love for God (Ross-shire, Great Britain: Christian Focus Publications, rpt. 2012), 7.
  2. Ibid.
  3. Ibid., 8.
  4. Ibid., 10.
  5. Ibid., 12.
  6. John Flavel, Keeping the Heart: How to Maintain Your Love for God (Ross-shire, Great Britain: Christian Focus Publication, rpt. 2012), 13.
  7. Ibid., 15.
  8. Ibid., 17.
  9. Ibid.
  10. Ibid., 18-21.
  11. Ibid., 32.
  12. Ibid., 22.
  13. Ibid., 24.
  14. Ibid., 32.
  15. Ibid., 33.
  16. Ibid., 35ff.
  17. Ibid., 41ff.
  18. Ibid., 46-47.
  19. Ibid., 48, 50ff.
  20. Ibid., 52.
  21. Ibid., 53.
  22. Ibid.
  23. Ibid., 62.
  24. Ibid., 66-67.
  25. Ibid., 69.
  26. Ibid., 71.
  27. Ibid., 81-84.
  28. Ibid., 91.
  29. Ibid., 92.
  30. Ibid., 107, 110.
  31. Ibid., 113-114.
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