OBLIGATION, in law, a term derived from the Roman law, in which obligatio signified a tie of law (vinculum iuris), 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 from contract, in the latter 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. But in legal systems, chiefly founded on Roman law, the original meanings remain. In English law obligation is used in at least four senses—(1) any duty imposed by law ; 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 and
fourth uses of the word are chiefly confined to the older writers. The party bound is still called the obligor, the party in whose favour the bond is made the obligee. 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 obliga tion (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.
American law is in general agreement with English. The term obligation is important in the U.S.A. from its use in art. i. s. Io of the constitution, "No state . . . shall pass any . . . law . . . impairing the obligation of contracts." This does not affect the power of Congress to pass such a law.