Charles Spurgeon once wrote, "You may think that it is easy to define faith, and so it is, but it is easier still to confuse people with your definition." Martin Luther defined faith as "a lively, reckless confidence in God." The Quaker scholar J. Elton Trueblood said, "Faith is not belief without proof, but trust without reservation." In her excellent book The Secret of a Happy Christian Life, in a very practical vein, Hannah Smith wrote, "Faith is the simplest and plainest thing in the world...it is simply believing God."