The appeal to authority, then, will not be an appeal to practice, but always an appeal to principle; and so we shall be saved from that danger of moral experiment, a danger that is so immensely great because the individual who has made the experiment has thereby very often spoilt himself. One cannot experiment in the moral life with the detachment that we use in science. I may try mixing a couple of fluids together to see what happens, and I can regard the result quite accurately; but I cannot try the experiment of stealing, or of murder, in order to see what the real moral value of the thing is, because in the process of doing the act I shall vitiate my own soul; here the material in which we experiment is itself the instrument by which we have to judge; and the man who has once done an evil thing himself, very seldom has the same clearness of vision concerning its good and evil as the man who has kept true to some lofty purpose. The mere experiment, the mere trying what it feels like to be a murderer—not that anyone would take so extreme an instance as that—is always a method condemned in advance to futility, because in the process of making the experiment we destroy our power of judging the result. We want therefore to rely upon some authority; being unable to experiment for ourselves, we must follow the general rule that I have stated; the authority to which we appeal must be an authority of principle and not of practice.
But what of the authority of our Lord Himself? To us who have accepted it, or who are trying to accept it, it is final; yet still, surely, in the spirit rather than in the letter. Why did He teach by a series of amazing paradoxes if it was not to prevent us setting up a code of rules as His legislation, if it was not to force us back upon the spirit of His teaching, behind the detailed regulations in which that spirit was embodied? Even here it is still true that the appeal is to the authority of His Spirit and not to that of detailed action or individual precept.
And beyond all this, it is certain that He Himself wins His authority by first submitting Himself to the moral judgment of His people. He rejects, in the second and third of the Messianic temptations after His baptism, the method of coercion. He rejects this, and stands before men submitting Himself to their moral judgment, to their conscience, to their capacity to understand pure goodness and love, as that capacity has grown through the civilisation which God Himself had guided as the preparation for His final revelation in His Son. So He submits Himself first of all to our moral judgment; and thus our conscience, coming down to us, as it does, out of the Divinely-guided history of the past, is the supreme authority; if we choose Him to be the Guide of our life it is because our conscience has first pronounced Him to be the highest and the holiest, which we must needs love when we see it.