In any case, you can't have effective allegory in times when people are swept this way and that by momentary convictions, because everyone will read it differently. You can't indicate moral values when morality changes with what is being done, because there is no accepted basis of judgment. And you cannot show the operation of grace when grace is cut off from nature or when the very possibility of grace is denied, because no one will have the least idea of what you are about.

Mystery and Manners: Occasional Prose