But it is equally true, my good friend, that the non-fulfilment of a promise is disagreeable to the promisee, and in so far it is an element of discord, and discord is the opposite of harmony. You need not look for harmony until people are disposed to be harmonious. But justice, or a close approximation thereto, can be secured even from ill-disposed people. I have no doubt of the right of any man to whom, for a consideration, a promise has been made, to insist, even by force, upon the fulfilment of that promise, provided the promise be not one whose fulfilment would invade third parties. And if the promisee has a right to use force himself for such a purpose, he has a right to secure such co-operative force from others as they are willing to extend. These others, in turn, have a right to decide what sort of promises, if any, they will help him to enforce. When it comes to the determination of this point, the question is one of policy solely; and very likely it will be found that the best way to secure the fulfilment of promises is to have it understood in advance that the fulfilment is not to be enforced. But as a matter of justice and liberty, it must always be remembered that a promise is a two-sided affair. And in our anxiety to leave the promisor his liberty, we must not forget the superior right of the promisee. I say superior, because the man who fulfils a promise, however unjust the contract, acts voluntarily, whereas the man who has received the promise is defrauded by its non-fulfilment, invaded, deprived of a portion of his liberty against his will.(51 ¶ 3)