mere
Pact or Convention could be the basis of a _plea_. It followed from
this, that though nobody could sue upon an agreement which he had not
taken the precaution to mature into a Contract by complying with the
proper forms, nevertheless a claim arising out of a valid contract
could be rebutted by proving a counter-agreement which had never got
beyond the state of a simple convention. An action for the recovery of
a debt could be met by showing a mere informal agreement to waive or
postpone the payment.

The doctrine just stated indicates the hesitation of the Praetors in
making their advances towards the greatest of their innovations. Their
theory of Natural law must have led them to look with especial favour
on the Consensual Contracts and on those Pacts or Conventions of which
the Consensual Contracts were only particular instances; but they did
not at once venture on extending to all Conventions the liberty of the
Consensual Contracts. They took advantage of that special
superintendence over procedure which had been confided to them since
the first beginnings of Roman law, and, while they still declined to
permit a suit to be launched which was not based on a formal contract,
they gave full play to their new theory of agreement in directing the
ulterior stages of the proceeding. But, when they had proceeded thus
far, it was inevitable that they should proceed farther. The
revolution of the ancient law of Contract was consummated when the
Praetor of some one year announced in his Edict that he would grant
equitable actions upon Pacts which had never been matured at all into
Contracts, provided only that the Pacts in question had been founded
on a consideration (_causa_). Pacts of this sort are always enforced
under the advanced Roman jurisprudence. The principle is merely the
principle of the Consensual Contract carried to its proper
consequence; and, in fact, if the technical language of the Romans had
been as plastic as their legal theories, these Pacts enforced by the
Praetor would have been styled new Contracts, new Consensual Contracts.
Legal phraseology is, however, the part of the law which is the last
to alter, and the Pacts equitably enforced continued to be designated
simply Praetorian Pacts. It will be remarked that unless there were
consideration for the Pact, it would continue _nude_ so far as the new
jurisprudence was concerned; in order to give it effect, it would be
necessary to convert it by a stip