So authority always in the end means weight—what carries weight with our judgment. We can weigh one authority against another; we may weigh the authority of one theologian with that of another by considering which has shown the greater knowledge of the subject in question and the sounder judgment in dealing with it. In moral questions we do as a matter of fact perpetually come back to the man of moral weight. And what constitutes his weight is to begin with a certain uprightness in his own character, and then a certain sympathy and insight which enables him to understand how he would apply to the circumstances of other people the principles by which he lives in his own. So, for example, Aristotle in the end determines all moral questions by reference to the standard which the man of moral sense would use; everything in the last resort is determined simply by his judgment. Virtue, he says, resides in a mean between two vicious extremes, and the mean is to be determined by a principle which the man of moral sense would use. Later on, after an interlude of two or three books wisely interpolated, he comes to ask, Who is the man of moral sense? and he turns out to be the man who has the right principle enabling him to determine the mean between vicious extremes; that is to say, that his standard of judgment in the end is simply the good, sensible man, and for practical purposes that does well enough, because for practical purposes we do know whose judgment we value, we do know who it is whose approval we should care to win, whose approval would of itself assure us that our conduct was right, and whose disapproval would of itself go far at least to assure us that our conduct was wrong, or at any rate that the matter needed careful reconsideration.
There is indeed another method than this of reliance upon the authority of a wise man, and it is represented by the other great thinker of Greece, by Plato. Plato’s ideal method in moral questions was to try to determine the purpose of the whole universe and then determine how in any given circumstances a man may serve that purpose. The basis of his morals, in other words, was what we should call theological; and so far as we are able to apply this, it is the only finally satisfactory method; so far as we can say that the principles of Christianity imperatively demand some particular action or attitude of mind, we shall not care how little other authority we can quote, but shall say that we can see quite clearly that our allegiance to Christ and His religion involves a certain point of view for us; and if no one else has taken that point of view, provided we can find no flaw in our reasoning, we shall say none the less, This is the point of view which we, as Christians, are bound to take.