Nexum, therefore, which originally signified a Conveyance of property, came insensibly to denote a Contract also, and ultimately so constant became the association between this word and the notion of a Contract, that a special term, Mancipium or Mancipatio, had to be used for the purpose of designating the true nexum or transaction in which the property was really transferred. Contracts are therefore now severed from Conveyances, and the first stage in their history is accomplished, but still they are far enough from that epoch of their development when the promise of the contractor has a higher sacredness than the formalities with which it is coupled. In attempting to indicate the character of the changes passed through in this interval, it is necessary to trespass a little on a subject which lies properly beyond the range of these pages, the analysis of Agreement effected by the Roman jurisconsults. Of this analysis, the most beautiful monument of their sagacity, I need not say more than that it is based on the theoretical separation of the Obligation from the Convention or Pact. Bentham and Mr. Austin have laid down that the "two main essentials of a contract are these: first, a signification by the promising party of his _intention_ to do the acts or to observe the forbearances which he promises to do or to observe. Secondly, a signification by the promisee that he _expects_ the promising party will fulfil the proffered promise." This is virtually identical with the doctrine of the Roman lawyers, but then, in their view, the result of these "significations" was not a Contract, but a Convention or Pact. A Pact was the utmost product of the engagements of individuals agreeing among themselves, and it distinctly fell short of a Contract. Whether it ultimately became a Contract depended on the question whether the law annexed an Obligation to it. A Contract was a Pact (or Convention) _plus_ an Obligation. So long as the Pact remained unclothed with the Obligation, it was called _nude_ or _naked_.