. 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
religion paved the way for much that was done presently in the name of
philosophy.

To the jurists of the seventeenth