religion paved the way for much that was done presently in the name of philosophy. To the jurists of the seventeenth and eighteenth centuries no distinction between natural obligations and civil obligations was maintainable since all natural rights or obligations must for the very reason that they were natural be legal also. If it was morally obligatory that one adhere to a pact, then it must be treated as a contract. However much systematized analytically, the Roman categories of contract did not deal with undertakings from this standpoint. What the jurists desired was not analytical categories but a principle upon which men were to be held or not to be held upon their promises. Thus the philosophy of contract, the principles underlying the binding force of promises and agreements, became the chief problem of philosophical jurisprudence of the seventeenth century, as interests of personality were the chief subject of discussion in the eighteenth century, and interests of substance, the philosophy of the law of property, the chief subject of discussion in the nineteenth century. The decisive element in seventeenth-century thought as to contract was the idea of natural law; the idea of deduction from the nature of man as a moral creature and of legal rules and legal institutions which expressed this ideal of human nature. But the idea was put to work upon existing materials and the result was a reciprocal influence of the conception of enforcing promises as such because morally binding, on the one hand, shaped to some extent by canon law and casuist discussions of what promises were binding in conscience and when, and the ideas of _nudum pactum_ and _causa debendi_ on the other hand. Roman law was assumed to be embodied reason. As D'Aguesseau put it, Rome was ruling by her reason, having ceased to rule by her authority. Hence all consideration of the subject starts with the assumption that there are morally naked agreements which for that reason are to be naked legally. Where there was an exchange of promises there was the authority of Justinian for enforcement (_synallagma_) and it was easy to find a reason in the analogy of exchange of property. Where something was exchanged for a promise, that something was a _causa debendi_. But suppose there was no exchange of promises nor was anything exchanged for the promise. There was nothing but a promise assented to. In Roman law this would have to take the form of a stipulation. In the Germanic law it would have required an oath or the form of a real transaction of pledge or exchange. At common law it required delivery of a sealed instrument. Clearly there was no moral efficacy inherent in these forms. Why should these "abstract" promises be enforced and not others? Should every such promise be enforced or should none be enforced without something in the way of exchange, or should such promises be classified for the purpose of enforcement, and if so, how?