What does it mean for believers to stand together for the gospel?
In simple terms, it means that while they might have other theological differences, they are united in affirming the gospel’s core tenants. Specifically, they agree that sinners are justified not by their own efforts, but by grace alone, through faith alone, in Christ alone.
It’s that last element in particular that offends and annoys our pluralistic, inclusive society. But as F. F. Bruce explains, the gospel’s exclusivity flows directly out of Christ’s nature in His incarnation.
He is, in fact, the only way by which men and women may come to the Father, there is no other way. If this seems offensively exclusive, let it be borne in mind that the one who makes this claim is the incarnate Word, the revealer of the Father. If God has no avenue of communication with mankind apart from his Word . . . mankind has no avenue of approach to God apart from that same Word, who became flesh and dwelt among us in order to supply such an avenue of approach.  F. F. Bruce, The Gospel of John (Grand Rapids: Eerdmans, 1983) 298.
Standing together for the gospel, then, is standing in agreement with Christ’s own assertions to His uniqueness: “I am the way, and the truth, and the life; no one comes to the Father but through Me” (John 14:6). It’s echoing the words Peter boldly proclaimed to the Sanhedrin, that “there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved” (Acts 4:12).
In spite of the innate exclusivity of the gospel, the world’s religions attempt to position themselves as co-laborers with Christianity. They might highlight similar stances on social issues, or simply try to identify a common enemy—whatever it takes to present the illusion of unity.
Worse still, many Christians are all too happy to lend those false religions spiritual credibility by operating as cobelligerents.
Such ecumenical partnerships require a muddying of doctrinal waters. Theological distinctives are downplayed or set aside in the name of unity, as both sides come to a polemical cease-fire in pursuit of a common goal.
The 1994 ecumenical treatise Evangelicals and Catholics Together: The Christian Mission in the Third Millennium (ECT) is a prime example. In an effort to kick-start “a springtime of world missions,” influential leaders from both faiths attempted to identify and affirm theological common ground for the sake of furthering the reach of the gospel (you can read the full document here).
In reality, they ignored centuries of church history and asserted vague platitudes about unity in Christ.
All who accept Christ as Lord and Savior are brothers and sisters in Christ. Evangelicals and Catholics are brothers and sisters in Christ. We have not chosen one another, just as we have not chosen Christ. He has chosen us, and he has chosen us to be his together (John 15). However imperfect our communion with one another, however deep our disagreements with one another, we recognize that there is but one church of Christ. There is one church because there is one Christ and the church is his body. However difficult the way, we recognize that we are called by God to a fuller realization of our unity in the body of Christ.
But what gospel were they uniting behind? Let’s not forget or ignore—as the signatories of ECT must have—that Catholic dogma pronounces anathema on anyone who preaches justification by faith alone. Here is the stark condemnation, spelled out by the Council of Trent:
If any one saith, that by faith alone the impious is justified; in such wise as to mean, that nothing else is required to co-operate in order to the obtaining the grace of Justification, and that it is not in any way necessary, that he be prepared and disposed by the movement of his own will; let him be anathema. (Canon IX)
If any one saith, that the justice received is not preserved and also increased before God through good works; but that the said works are merely the fruits and signs of Justification obtained, but not a cause of the increase thereof; let him be anathema. (Canon XXIV)
How can evangelicals set aside such a clear repudiation of justification by faith in the name of unity? How can the two sides claim unity in Christ when their views of Christ’s work are so thoroughly divergent? Moreover, what good is that unity once the doctrinal differences have been swept under the rug?
But that wasn’t even the worst aspect of ECT. In addition to propping up the frail façade of unity, the document also prohibited attempts to “win ‘converts’ from one another’s folds,” downplaying such efforts as “sheep stealing” that would “undermine the Christian mission.” It further argued that,
in view of the large number of non-Christians in the world and the enormous challenge of our common evangelistic task, it is neither theologically legitimate nor a prudent use of resources for one Christian community to proselytize among active adherents of another Christian community.
In one fell swoop, ECT declared the entire Catholic Church—which today claims more than a 1.25 billion followers worldwide—off limits from the gospel, consigning them to Rome’s demonic heresies. Why would believers champion such feeble unity to the exclusion of so vast a mission field?
Ecumenism is not true unity. It’s a lie agreed upon—one that inoculates lost souls to the life-transforming truth of the gospel.
And as the world becomes increasingly pluralistic, believers need to be committed to protecting the purity of the gospel, resisting the world’s urging to mix it with error. We need to keep clear in our minds the black and white distinction between truth and error, and not succumb to the influence of an increasingly gray world. Here’s how John MacArthur describes the mindset believers need to foster:
Christians preach an exclusive Christ in an inclusive age. Because of that, we are often accused of being narrow-minded, even intolerant. Many paths, it is said, lead to the top of the mountain of religious enlightenment. How dare we insist that ours is the only one? In reality, however, there are only two religious paths: the broad way of works salvation leading to destruction, and the narrow way of faith in the only Savior leading to eternal life (Matthew 7:13-14). Religious people are on either one or the other. John MacArthur, The MacArthur New Testament Commentary: Acts 1-12 (Chicago: Moody Publishers, 1994), 135-136.
Put simply, standing together for the gospel means standing together against ecumenical movements that assault and betray the exclusivity of Christ.