But the latter was so thoroughly established as a formal transaction that the case of a loan of money, analytically a real contract, preserved the incidents of the strict law. Moreover certain pacts, _pacta adiecta_, _pacta praetoria_, became actionable which do not fit into the analytical scheme of the Institutes. For example, a _causa_ or reason for enforcing these pacts was found in their being incidental to something else or in a pre-existing natural obligation which they undertook to satisfy. There still remained natural obligations which had not been given legal efficacy as the basis of actions. The mere will of the person who undertook or the claim of the promisee was not a reason for enforcing. Yet in reason they were morally binding and the legal and moral should coincide. Hence they might be used defensively or as the basis of a set-off. Meanwhile the forms of stipulation and of literal contract had been reduced to their lowest terms by conceiving them in terms of substance, and taking orally expressed agreement to be the substance of the one and writing to be the substance of the other. The results have defied analysis although the best that juristic ingenuity could do has been expended upon them for centuries. In the Middle Ages primitive ideas came back for a time through Germanic law. General security in its lowest terms of peace and order was the pressing social interest. There was little commercial activity. The civilization of the time did not involve the corollaries of our jural postulate. Religiously sanctioned undertakings by promissory oath and real transactions of pledge of person or property and of exchange gave rise to a simple system of formal undertakings. Out of these came a theory of _causa debendi_, or reason for owing the promised performance, which has had a profound influence upon subsequent thinking. The Roman _causa ciuilis_ was a legal reason for enforcing a pact. Under the influence of the Germanic idea _causa_ becomes a reason for making the pact, the good reason for making it furnishing a sufficient reason for enforcing it. For a time it seemed that the church might succeed in establishing a jurisdiction over promises. Oaths and vows involved religious duties and might well be claimed as the province of the spiritual. But the moral obligation of pacts, binding the conscience of a Christian, might also be cognizable by a zealous corrector of the conduct of the faithful for their soul's welfare. Had not the power of the canon law broken down and the law of the state developed rapidly in respect of the security of transactions after the sixteenth century, the law of contracts might have grown along religious instead of along philosophical lines, and perhaps not to its advantage. As it is, one need but read Doctor and Student with the title _de pactis_ of the _Corpus Iuris Canonici_ and casuist writings as to the moral efficacy of promises before him, to see that