is proved by the facts that mistakes do creep into works of science, however carefully examined, and that more than one book with an _imprimatur_ has, none the less, found its way on to the _Index_. Before leaving this branch of the subject one cannot refrain from calling attention to another point. How often in advertisements of books do we not see quotations from reviews in authoritative journals--a medical work from the _Lancet_, a physical or chemical from _Nature_? Frequently too we see "Mr. So-and-So, the well-known authority on the subject, says of this book, etc., etc." What are all these authoritative commendations but an _imprimatur_ up to date? Passing from the _imprimatur_ to a closer consideration of our subject, it is above all things necessary to take the advice of Samuel Johnson and clear our minds of cant. Every person in this world--save perhaps a Robinson Crusoe on an otherwise uninhabited island, and he only because of his solitary condition--is in bondage more or less to others; that is to say, has his freedom more or less interfered with. That this interference is in the interests of the community and so, in the last analysis, in the interests of the person interfered with himself, in no way weakens the argument; it is rather a potent adjuvant to it. However much I may dislike him and however anxious I may be to injure him, I may not go out and set fire to my neighbour's house nor to his rick-yard, unless I am prepared to risk the serious legal penalties which will be my lot if I am detected in the act. I may not, if I am a small and active boy, make a slide in the public street in frosty weather, unless I am prepared--as the small boy usually is--to run the gauntlet of the police. In a thousand ways my freedom, or what I call my freedom, is interfered with: it is the price which I pay for being one item of a social organism and for being in turn protected against others, who, in virtue of that protection, are in their turn deprived of what they might call their liberty.