Likewise in civil-law countries the enforcing machinery is modern and adequate. The oldest method of enforcement in Roman law was seizure of the person, to coerce satisfaction or hold the promisor in bondage until his kinsmen performed the judgment. Later there was a pecuniary condemnation or, as we should say, a money judgment in all cases, enforced in the classical law by universal execution or, as we should say, by involuntary bankruptcy. But along with this remedy specific relief grew up in the _actio arbitraria_, a clumsy device of specific performance on the alternative of a heavy money condemnation, which repeated itself in Pennsylvania before equity powers were given the courts, and is substantially repeating in our federal courts in their attempts to apply equitable relief to torts committed in foreign jurisdictions. The civil law developed, or perhaps the canon law developed and the civil law took over, an _actio ad implendum_ or action to require performance, with natural execution, that is a doing by the court or its officers at the expense of the defendant, of that to which he is bound as ascertained by the judgment. In general in civil-law countries today what we call specific performance is the rule. A money reparation for breach of contract is the exceptional remedy. It is only when for some reason specific relief is impracticable or inequitable, as in contracts of personal service, that money relief is resorted to. In countries governed by the common law we do not secure this interest so completely nor so effectively. For one thing we do not recognize as legally enforceable all intentional promises intended to be binding upon the promisor. Many technical rules as to consideration, rules having chiefly a historical basis, stand in the way. Many jurisdictions have abolished private seals and have made no provision for formal gratuitous or abstract promises. Moreover, we do not give specific relief ordinarily but only exceptionally where pecuniary relief is considered inadequate. Hence in the great majority of cases the promisee cannot compel performance in specie. If we look into the reasons for this wide and effective enforcement of promises in the one system and narrower and less effective enforcement in the other, we come in both cases upon a mixture of historical background and philosophical reasoning, each influencing the other and neither governing the subject completely. Philosophical theories have arisen to explain existing rules and have been the basis of new rules and of remaking of old ones. But they have been the means also, at times, of intrenching the rules they sought to explain and of fastening on the law doctrines of which it were better rid. Nowhere is the reciprocal action of legal rules and philosophical theories more strikingly manifest than in our law of contractual liability.