Furthermore, there is to be recognized the legal norm that contracts must be lived up to. Obligation comes into existence when obligations are "consciously and voluntarily assumed";[698] and the other party thus acquires "a right."[699] To be sure, the obligatory force of contract is not without bounds. "Contract is a very serviceable and most important tool, but its usefulness has its limits; no man can employ it for the abdication of his manhood";[700] therefore "the constituting of an association in which each member waives the right of secession would be a mere _form_."[701] Furthermore, no one can employ it for the invasion of third parties; therefore a promise "whose fulfilment would invade third parties"[702] would be invalid.--"I deem the keeping of promises such an important matter that only in the extremest cases would I approve their violation. It is of such vital consequence that associates should be able to rely upon each other that it is better never to do anything to weaken this confidence except when it can be maintained only at the expense of some consideration of even greater importance."[703] "The man who has received a promise is defrauded by its non-fulfilment, invaded, deprived of a portion of his liberty against his will."[704] "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."[705] 4.--THE STATE I. _With regard to every man's self-interest, especially on the basis of the law of equal liberty, Tucker rejects the State; and that universally, not merely for special circumstances determined by place and time._ For the State is "the embodiment of the principle of invasion."[706]