I mean by injustice, in this connection, the behavior of a man who does not take care to keep controversy distinct from discussion; a man who forgets that in controversy he may play about and trip up his opponent as often as he can, but that in discussion he must be serious, he must keep on helping his opponent to his feet again, and point out to him only those of his slips which are due to himself or to the intellectual society which he has previously frequented.