Lesslie Newbigin, in his book The Reunion of the Church, challenged the Church to be on mission:

“The responsibility of the church is to declare to each generation what is the faith… This is always a fresh task in every generation… No verbal statement can be produced which relieves the Church of the responsibility continually to re-think and re-state its message. No appeal to creeds and confessions can alter the fact that the Church has to state in every new generation how it interprets the historic faith, and how it relates it to the new thought and experience of its time… Nothing can remove from the Church the responsibility for stating now what is the faith. It belongs to the essence of a living church that it should be able and willing to do so.”

NOTE: Those unfamiliar with Newbigin may appreciate this article by Bruce Ashford: How A Man Named Lesslie Changed the Way I Think.