There is no question whatsoever, that is of greater importance to mankind, and that it more concerns every individual person to be well resolved in, than this, what are the distinguishing qualifications of those who are in favor with God, and entitled to his eternal rewards? Or, which comes to the same thing, What is the nature of true religion? and wherein do lie the distinguishing notes of that virtue and holiness, that is acceptable in the sight of God.
WJE 2:84 (Preface to Religious Affections)