God alone, who has told us that this gospel of the kingdom shall be preached in the whole world for a testimony unto all the nations, will know when that objective has been accomplished. But I do not need to know. I know only one thing: Christ has not yet returned; therefore, the task is not yet done. When it is done, Christ will come. Our responsibility is not to insist on defining the terms of our task; our responsibility is to complete it. So long as Christ does not return, our work is not done. Let us get busy and complete our mission!

—George Ladd, U.S. author, professor, and theologian (1911-1982)