and even without such voluntary release, there are perhaps no contracts or engagements, except those that relate to money or money's worth, of which one can venture to say that there ought to be no liberty whatever of retractation.
それに、自発的契約解除がなくても、金銭や金銭的価値に関する以外で、いかなる撤回の自由もあってはならないと敢て主張しうるような契約は、おそらく全くないでしょう。 - John Stuart Mill『自由について』