I cannot speak of religion without lamenting that, among so many pretenders of it, so few understand what it means. Some place it in the understanding, orthodox notions and opinions; and all the account they can give of their religion is that they are of this or the other persuasion, and have joined themselves to one of those many sects whereinto Christendom is most unhappily divided. Others place it in the outward man, in a constant course of external duties and a model of performances; if they live peaceably with their neighbors, keep a temperate diet, observe the returns of worship, frequenting the church and their closet, and sometimes extend their hands to relieve the poor, they think they have sufficiently acquitted themselves. Others again put all religion in the affections, in rapturous heats and ecstatic devotion; and all they aim at is to pray with passion, to think of heaven with pleasure, and to be affected with those kind and melting expressions wherewith they court their Savior till they persuade themselves that they are mightily in love with him. And from this they assume a great confidence of their salvation, which they esteem the chief of Christian graces.
Thus are those things which have any resemblance of piety, and at best are but means of obtaining it, or particular exercises of it, frequently mistaken for the whole of religion….
But certainly religion is quite another thing; and they who are acquainted with it will entertain far different thoughts, and disdain all those shadows and false imitations of it. They know by experience that true religion is a union of the soul with God, a real participation in the divine nature, the very image of God drawn upon the soul. In the apostle’s words, it is “Christ formed in you.”
The Life of God in the Soul of Man