In the developed Roman law, the Convention, as soon as it was completed, was, in almost all cases, at once crowned with the Obligation, and so became a Contract; and this was the result to which contract-law was surely tending. But for the purpose of this inquiry, we must attend particularly to the intermediate stage--that in which something more than a perfect agreement was required to attract the Obligation. This epoch is synchronous with the period at which the famous Roman classification of Contracts into four sorts--the Verbal, the Literal, the Real, and the Consensual--had come into use, and during which these four orders of Contracts constituted the only descriptions of engagement which the law would enforce. The meaning of the fourfold distribution is readily understood as soon as we apprehend the theory which severed the Obligation from the Convention. Each class of contracts was in fact named from certain formalities which were required over and above the mere agreement of the contracting parties. In the Verbal Contract, as soon as the Convention was effected, a form of words had to be gone through before the vinculum juris was attached to it. In the Literal Contract, an entry in a ledger or table-book had the effect of clothing the Convention with the Obligation, and the same result followed, in the case of the Real Contract, from the delivery of the Res or Thing which was the subject of the preliminary engagement. The contracting parties came, in short, to an understanding in each case; but, if they went no further, they were not _obliged_ to one another, and could not compel performance or ask redress for a breach of faith. But let them comply with certain prescribed formalities, and the Contract was immediately complete, taking its name from the particular form which it had suited them to adopt. The exceptions to this practice will be noticed presently.