Believe it or not, missionaries all too often don't have this assumed key to effectiveness in their toolbox. It's not enough to have a passion for missionary ministry! Even sincere candidates (and missionaries on the field!) have such a simplistic understanding of the Gospel and of the Bible that they freeze up if called on to explain the storyline of the Bible or find a reference in one of the Minor Prophets. Having a good grasp of Bible content, the interpretation of Scripture, contexts, biblical history, and application of the sufficiency of Scripture are important skills that are used often in the challenging questions and spiritual discipline of people on the mission field. Better to get in here than to lack it there.