Who, then, can prove that I am the proper person to impose, by my own choice, my conception of man upon mankind? I shall never find any proof whatever; there will be no sign to convince me of it. If a voice speaks to me, it is still I myself who must decide whether the voice is or is not that of an angel. If I regard a certain course of action as good, it is only I who choose to say that it is good and not bad.