Now, let this new experience of moral power and spiritual insight express itself, as it normally will, in a more holy and more useful life, in the appropriate terms of action. There you get that confession of experience which we call character. Or let it express itself in the appropriate emotions of joy and awe and reverence so that, like Ray Palmer, the convert writes an immortal hymn, or a body of converts like the early church produces the _Te Deum_. There is the confession of experience in worship. Or let a man filled with this new life desire to understand it; see what its implications are regarding the nature of God, the nature of man, the place of Christ in the scale of created or uncreated Being. Let him desire to thus conserve and interpret that he may transmit this new experience. Then he will begin to define it and to reduce it, for brevity and clearness, to some abstract and compact formula. Thus he will make a confession of experience in doctrine. Doctrines, then, are not arbitrary but natural, not accidental but essential. They are the hypotheses regarding the eternal nature of things drawn from the data of our moral and spiritual experience. They are to religion just what the science of electricity is to a trolley car, or what the formula of evolution is to natural science, or what the doctrine of the conservation of energy is, or was, to physics. Doctrines are signposts; they are placards, index fingers, notices summing up and commending the proved essences of religious experience. Two things are always true of sound doctrine. First: it is not considered to have primary value; its worth is in the experience to which it witnesses. Second: it is not fixed but flexible and progressive. Someone has railed at theology, defining it as the history of discarded errors. That is a truth and a great compliment and the definition holds good of the record of any other science.