We affirm that the gospel of Jesus Christ is the boundary of Christian faith (1 Cor. 15). We also affirm that to ignore this boundary by granting Christian recognition to those who deny the gospel is to demean the gospel itself (2 John 1:10).
We deny that Christian fellowship is possible with those who deny the fundamentals of the gospel, including (among others) the inerrancy of Scripture, the virgin birth, the deity of Christ, his sacrificial atonement, and justification by grace alone through faith alone in Christ alone.
Here is found the most fundamental difference between liberalism and Christianity—liberalism is altogether in the imperative mood, while Christianity begins with a triumphant indicative; liberalism appeals to man’s will, while Christianity announces,
first, a gracious act of God.
—J. Gresham Machen, Christianity and Liberalism
Christianity is irreducibly doctrinal. It is always more than doctrine, but it is never less. The reason that Christianity cannot fail to be doctrinal is that the gospel always involves doctrine. Paul’s example bears out this assertion: when he defines the gospel, he appeals to two elements. The first is a sequence of historical events, namely, that Jesus Christ died (the evidence for which is that he was buried), and Jesus Christ rose again (the evidence for which is that he was seen by witnesses). Paul’s central argument in 1 Corinthians 15 is that if the historicity of these events is denied, the gospel falls; without them, Christian hope vanishes. Without these events, Christianity cannot exist.
These events, however, are not the whole gospel. Hundreds of criminals suffered the same fate as Jesus of Nazareth. Furthermore, even if the dead body of Jesus were to be revived, that would be merely a novelty of history unless it was theologically interpreted. Paul states the correct interpretation: Jesus died for our sins in accordance with the Scriptures. He was raised on the third day in accordance with the Scriptures.
These explanations are filled with importance. To say that Jesus died for our sins is to affirm that 1) God possesses the authority to say what is sin, 2) we are sinners, 3) sin merits judgment, and 4) there is One qualified to take that judgment in our place. To be qualified to bear our sins, the Bearer must be 1) without sin, 2) like us, and 3) of infinite worth.
Such explanations could continue. What should be clear, however, is that Paul’s brief summary of the gospel, which is the essence of the Christian message, is unavoidably doctrinal. To deny the historicity of the events of the gospel is to deny the gospel. To deny the biblical interpretation of those events is also to deny the gospel.
The gospel is what unites Christians. Where the gospel is denied, either explicitly or implicitly, no true fellowship (koinonia) exists. To claim to have Christian fellowship with those who deny the gospel is to demean the gospel, to remove it from its rightful place as the boundary of Christian fellowship. Those who demean the gospel ought never be looked to as models of wise Christian living or leadership.
In terms of Christian fellowship, then, our commitment to the gospel always is more central than our commitment to specific worship forms. For example, beautiful worship does not somehow make a denial of justification through faith alone permissible. Some churches have maintained “traditional” worship practices while abandoning the gospel. They are not fitting objects of Christian recognition.