John Newton, writing in a letter to a correspondent on controversy (Works of John Newton, 1:270-272), suggests that of all people Calvinists should be the most humble and gentle. But sadly this is not always the case:
Of all people who engage in controversy, we, who are called Calvinists, are most expressly bound by our own principles to the exercise of gentleness and moderation. . . .
The Scriptural maximum, that “The wrath of man worketh not the righteousness of God,” is verified by daily observation. If our zeal is embittered by expressions of anger, invective, or scorn, we may think we are doing service to the cause of truth, when in reality we shall only bring it into discredit. . . .
Whatever it be that makes us trust in ourselves that we are comparatively wise or good, so as to treat those with contempt who do not subscribe to our doctrines, or follow our party, is a proof and fruit of a self-righteous spirit. Self-righteousness can feed upon doctrines, as well as upon works; and a man may have the heart of a Pharisee, while his head is stored with orthodox notions of the unworthiness of the creature and the riches of free grace.
Newton himself is not against controversy and polemics; he sees it as an essential activity post-fall and pre-eschaton:
It seems a laudable service to defend the faith once delivered to the saints; we are commanded to contend earnestly for it, and to convince gainsayers. If ever such defences were seasonable and expedient, they appear to be so in our day, when errors abound on all sides, and every truth of the Gospel is either directly denied, or grossly misrepresented.
But we must be careful to guard our hearts and to watch our tongues:
And yet we find but very few writers of controversy who have not been manifestly hurt by it. Either they grow in a sense of their own importance, or imbibe an angry contentious spirit, or they insensibly withdraw their attention from those things which are the food and immediate support of the life of faith, and spend their time and strength upon matters which at most are but of a secondary value.
This shews, that, if the service is honourable, it is dangerous. What will it profit a man if he gains his cause and silences his adversary, if at the same time he loses that humble, tender frame of spirit in which the Lord delights, and to which the promise of his presence is made! Your aim, I doubt not, is good; but you have need to watch and pray, for you will find Satan at your right hand to resist you: he will try to debase your views; and though you set out in defence of the cause of God, if you are not continually looking to the Lord to keep you, it may become your own cause, and awaken in you those tempers which are inconsistent with true peace of mind, and will surely obstruct communion with God.
Be on your guard against admitting any thing personal into the debate. If you think you have been ill treated, you will have an opportunity of shewing that you are a disciple of Jesus, who, “when he was reviled, reviled not again; when he suffered, he threatened not.” This is our pattern, thus we are to speak and write for God, “not rendering railing for railing, but, contrariwise, blessing; knowing that hereunto we are called.”
The wisdom that is from above is not only pure, but peaceable and gentle; and the want [i.e., lack] of these qualifications, like the dead fly in the post of ointment, will spoil the savour and efficacy of our labours. If we act in a wrong spirit, we should bring little glory to God, do little good to our fellow-creatures, and procure neither honour nor comfort to ourselves.
If you can be content with shewing your wit, and gaining the laugh on your side, you have an easy task; but I hope you have a far nobler aim, and that, sensible of the solemn importance of Gospel truths, and the compassion due to the souls of men, you would rather be a mean of removing prejudices in a single instance, than obtain the empty applause of thousands. Go forth, therefore, in the name and strength of the Lord of Hosts, speaking the truth in love; and may he give you a witness in many hearts, that you are taught of God, and favoured with the unction of his Holy Spirit.
In particular, Newton offers this practical advice for critiquing someone’s theology:
As to your opponent, I wish, that, before you set pen to paper against him, and during the whole time you are preparing your answer, you may commend him by earnest prayer to the Lord’s teaching and blessing. This practice will have a direct tendency to conciliate your heart to love and pity him; and such a disposition will have a good influence upon every page you write.
If you account him a believer, though greatly mistaken in the subject of debate between you, the words of David to Joab, concerning Absalom, are very applicable: “Deal gently with him for my sake.” The Lord loves him and bears with him; therefore you must not despise him, or treat him harshly. The Lord bears with you likewise, and expects that you should shew tenderness to others, from a sense of the much forgiveness you need yourself.
In a little while you will meet in heaven; he will then be dearer to you than the nearest friend you have upon earth is to you now. Anticipate that period in your thoughts; and though you may find it necessary to oppose his errors, view him personally as a kindred soul, with whom you are to be happy in Christ for ever.
But if you look upon him as an unconverted person, in a state of enmity against God and his grace, (a supposition which, without good evidence, you should be very unwilling to admit,) he is a more proper object of your compassion than your anger. Alas! “he knows not what he does.” But you know who has made you to differ. If God, in his sovereign good pleasure, had so appointed, you might have been as he is now; and he, instead of you, might have been set for the defence of the Gospel. You were both equally blind by nature. If you attend to this, you will not reproach or hate him, because the Lord has been pleased to open your eyes, and not his.