Questions of practical morals raise more difficult problems than questions of mere opinion.  The thugs honestly believe it their duty to commit murders, but the government does not acquiesce.  The conscientious objectors honestly hold the opposite opinion, and again the government does not acquiesce.  Killing is a state prerogative; it is equally criminal to do it unbidden and not to do it when bidden.  The same applies to theft, unless it is on a large scale or by one who is already rich.  Thugs and thieves are men who use force in their dealings with their neighbors, and we may lay it down broadly that the private use of force should be prohibited except in rare cases, however conscientious may be its motive.  But this principle will not justify compelling men to use force at the bidding of the state, when they do not believe it justified by the occasion.  The punishment of conscientious objectors seems clearly a violation of individual liberty within its legitimate sphere.

It is generally assumed without question that the state has a right to punish certain kinds of sexual irregularity.  No one doubts that the Mormons sincerely believed polygamy to be a desirable practice, yet the United States required them to abandon its legal recognition, and probably any other Christian country would have done likewise.  Nevertheless, I do not think this prohibition was wise.  Polygamy is legally permitted in many parts of the world, but is not much practised except by chiefs and potentates.  If, as Europeans generally believe, it is an undesirable custom, it is probable that the Mormons would have soon abandoned it, except perhaps for a few men of exceptional position.  If, on the other hand, it had proved a successful experiment, the world would have acquired a piece of knowledge which it is now unable to possess.  I think in all such cases the law should only intervene when there is some injury inflicted without the consent of the injured person.

It is obvious that men and women would not tolerate having their wives or husbands selected by the state, whatever eugenists might have to say in favor of such a plan.  In this it seems clear that ordinary public opinion is in the right, not because people choose wisely, but because any choice of their own is better than a forced marriage.  What applies to marriage ought also to apply to the choice of a trade or profession; although some men have no marked preferences, most men greatly prefer some occupations to others, and are far more likely to be useful citizens if they follow their preferences than if they are thwarted by a public authority.