There is another statement of Durham's I need to dig out, that essentially says, an error that is wrong to split a church over, is wrong to continue to maintain division over. We have a responsibility to union as well as to unity in doctrine. The things that divide for instance, the OPC and PCA, are small; those between the small EP Presbyterians even smaller. Now, some, like the PCA and OPC are even united in their error since they allow antiSabbatarianism. That is wrong and needs reforming; but so is division. I'm not saying one has to merge but one could envision denominations already close in doctrine coming into union in a super synod line NAPARC with actual governing force over serious error may come up to it. After all that really is only what a biblical synod does (Acts 15).
Here is the statement I had in mind in the previous post from Durham on necessity of union. From an old Facebook post.
There is not an established church about which James Durham could direct this today I suppose since he died in 1658, but surely there is application for the faithful reformed churches after centuries of denominationalism?
An absolute necessity laid upon a rent church to unite
1. The first general ground, which we take for granted, is this: that by way of precept there is an absolute necessity of uniting laid upon the church, so that it falls not under debate ‘Whether a church should continue divided or united in the Theses?’ more than it falls under debate whether there should be preaching, praying, keeping of the Sabbath, or any other commanded duty; seeing that union is both commanded as a duty, and commended, as eminently tending to the edification of the church, and therefore is so frequently joined with edification. Nor is it to be asked by a church, what is to be done for the church’s good in a divided way, thereby supposing a dispensation, as it were, to be given to division, and a forbearing of the use of means for the attaining thereof; or rather supposing a stating or fixing of division, and yet notwithstanding thereof, thinking to carry on edification. It is true, where union cannot be attained among orthodox ministers, that agree in all main things (for of such only we speak), ministers are to make the best use of the opportunities they have, and during that to seek the edification of the church. Yet, that men should by agreement state a division in the church, or dispense therewith and prefer the continuing of division, as fitter for edification than union, we suppose is altogether unwarrantable.
(1) Because that is not the Lord’s ordinance, and therefore cannot be gone about in faith, nor in it can the blessing be expected, which the Lord commands to those that are in unity (Ps. 133). (2) Because Christ’s church is but one body, and this were deliberately to alter the nature thereof. And although those who deny this truth may admit of division, yea, they cannot have union, that is proper church union, which is union in government, sacraments, and other ordinances, because union or communion in these results from this principle. Yet it is impossible for those that maintain that principle of the unity of the catholic visible church, to own a divided way of administrating government or other ordinances, but it will infer either that one party has no interest in the church, or that one church may be many, and so, that the unity thereof in its visible state is to no purpose. This then we take for granted. And though possibly it is not in all cases attainable, because the fault may be upon one side, who possibly will not act unitedly with others, yet is this still to be endeavored, and every opportunity to be taken hold of for promoting of the same.
James Durham, Concerning Scandals (Naphtali Press, 1990), 262–263. From part four: Concerning Scandalous Divisions, chapter four, General Grounds Leading to Unity. Durham spends 125 pages on this subject of the sin and cure of church divisions.