OBLIGATION  , in

law, a term derived from the Roman law, in which obligatio signified a tie of law (vinculum juris) whereby one person is bound to perform or forbear some act for another . The obligatio of Roman law arose either from voluntary acts or from circumstances to which legal consequences were annexed . In the former case it was said to arise ex contractu, from contract, in the latter quasi ex contractu, ex delicto, or quasi ex delictothat is to say, from tort, or from acts or omissions to which the law practically attached the same results as it did to contract or tort . Obligatio was used to denote either end of the legal chain that bound the parties, the right of the party who could compel fulfilment of the obligatio, the creditor, or the duty of the party who could be compelled to fulfilment, the debitor . In English law obligation has only the latter sense . Creditor and debtor have also lost their Roman law signification; they have been narrowed to mean the parties where the obligation is the payment of a sum of money . In English law obligation is used in at least four senses—(1) any duty imposed by law; (2) the special duty created by a vinculum juris; (3) not the duty, but the evidence of the duty—that is to say, an instrument under seal, otherwise called a bond; (4) the operative part of a bond . The third use of the word is chiefly confined to the older writers . Simplex and duplex obligatio were the old names for what are now more commonly called a single and a double or conditional bond . The party bound is still called the obligor, the party in whose favour the bond is made the obligee . The fourth, like the third, is a use scarcely found except in the older writers . The word " bond " is of course a mere translation of obligatio .

Obligations may be either perfect or imperfect . A perfect obligation is one which is directly enforceable by legal proceedings; an imperfect or moral obligation (the naturalis obligatio of Roman law) is one in which the vinculum juris is in some respects incomplete, so that it cannot be directly enforced, though it is not entirely destitute of legal effect . A perfect obligation may become imperfect by

lapse of time or other means, and, conversely, an imperfect obligation may under certain circumstances become perfect . Thus a debt may be barred by the Statute of Limitations and so cease to be enforce-able . The obligation, however, remains, though imperfect, for if there be a subsequent acknowledgment by the debtor, the debt revives, and the imperfect obligation becomes again perfect . At one period there was some doubt among English lawyers whether a moral obligation could be regarded as sufficient consideration for a contract; it has now, however, been long decided that it cannot be so regarded . American law is in general agreement with English, except in the case of Louisiana, where the terms obligor and obligee are used in as wide a sense as the debitor and creditor of Roman law . By art . 3522 of the Louisiana civil code obligor or debtor means the person who has engaged to perform some obligation, obligee or creditor the person -in favour of whom some obligation is contracted, whether such obligation be to pay money or to do or not to do something . The term obligation is important in America from its use in art. i. s. ro of the constitution of the United States, "No state . . . shall pass any ... law . . . impairing the obligation of contracts." This does not affect the power of Congress to pass such a law .

Contracts between private individuals are of course within the

provision . So are private conveyances, charters of private corporations and statutory and other grants by a state . On the other hand, marriage and divorce, and arrangements which are political in their nature, such as charters of municipal corporations, licences to carry on particular trades or regulations of police are not within the provision . In order to fall within it, the law must act upon the terms of the agreement, and not merely upon the mode of procedure . If it act not upon the terms but upon the remedy, it impairs the obligation if it purport to be retrospective, but it is valid so far as it applies to subsequent contracts .