An orator, whose purpose is to persuade men, must speak the things they wish to hear, an orator, whose purpose is to move men, must also avoid disturbing the emotional effect by any obtrusion of intellectual antagonism, but an author, whose purpose is to instruct men, who appeals to the intellect, must be careless of their opinions and think only of truth. It will often be a question when a man is or is not wise in advancing an unpalatable opinion, or in preaching heresies. But it can never be a question that a man should be silent if unprepared to speak the truth as he conceives it. Deference to popular opinion is one great source of bad writing and is all the more disastrous because the deference is paid to some purely hypothetical requirement. When a man fails to see the truth of certain generally accepted views, there is no law compelling him to provoke animosity by announcing his dissent. He may be excused if he shrink from the lurid glory of martyrdom. He may be justified in not placing himself in a position of singularity. He may even be commended for not helping to perplex mankind with doubts which he feels to be founded on limited and possibly erroneous investigation. But if allegiance to truth lays no stern command upon him to speak out his immature dissent, it does lay a stern command not to speak out hypocritical assent. There are many justifications of silence, there can be none of insincerity. A man who dissents with generally accepted views ______.