Lesslie Newbigin writes:
Once the gospel is preached and there is a community which lives by the gospel, then the question of the ultimate meaning of history is posed and other messiahs appear. So the crisis of history is deepened (The Gospel in a Pluralistic Society, [Grand Rapids: Baker, 1989], 122, paragraphing mine).
The advance of the gospel deepens the crisis of history. Newbigin's explanation here is fascinating. Before people are confronted with the gospel, we are unaware of the right question to ask. The gospel intrudes with both the question and answer, however, the answer is only an answer to those who believe.
Even if the answer is not embraced, the question is still there. And if the question is still there, those who don't believe must find another answer. Unbelief is not isolated once you're confronted with the gospel. You cannot just reject Jesus, you must attempt to replace him. So the gospel advances, unbelief occurs, false-messiahs appear, and thus the crisis of history deepens.
The world's religious scene is increasingly becoming more complex. One implication of this complexity is the need for the Church to fulfill her calling as the pillar and buttress of truth (1 Timothy 3:15).
Now this sounds established and formal, even institutional, and I hope it doesn't make you squirm. Sound doctrine is non-negotiable for gospel communities, despite how missional they may be (Titus 1:5, 9). We can call the Church's mission an adventure if we choose, but if we're not grounded and committed to what's in step with the trustworthy word as taught, we definitely can't call it anything to do with the New Testament.