The Contract which stands next in historical succession, the Real Contract, shows a great advance in ethical conceptions. Whenever any agreement had for its object the delivery of a specific thing--and this is the case with the large majority of simple engagements--the Obligation was drawn down as soon as the delivery had actually taken place. Such a result must have involved a serious innovation on the oldest ideas of Contract; for doubtless, in the primitive times, when a contracting party had neglected to clothe his agreement in a stipulation, nothing done in pursuance of the agreement would be recognised by the law. A person who had paid over money on loan would be unable to sue for its repayment unless he had formally _stipulated_ for it. But, in the Real Contract, performance on one side is allowed to impose a legal duty on the other--evidently on ethical grounds. For the first time then moral considerations appear as an ingredient in Contract-law, and the Real Contract differs from its two predecessors in being founded on these, rather than on respect for technical forms or on deference to Roman domestic habits. We now reach the fourth class, or Consensual Contracts, the most interesting and important of all. Four specified Contracts were distinguished by this name: Mandatum, _i.e._ Commission or Agency; Societas or Partnership; Emtio Venditio or Sale; and Locatio Conductio or Letting and Hiring. A few pages ago, after stating that a Contract consisted of a Pact or Convention to which an Obligation had been superadded, I spoke of certain acts or formalities by which the law permitted the Obligation to be attracted to the Pact. I used this language on account of the advantage of a general expression, but it is not strictly correct unless it be understood to include the negative as well as the positive. For, in truth, the peculiarity of these Consensual Contracts is that _no_ formalities, are required to create them out of the Pact. Much that is indefensible, and much more that is obscure, has been written about the Consensual Contracts, and it has even been asserted that in them the _consent_ of the Parties is more emphatically given than in any other species of agreement. But the term Consensual merely indicates that the Obligation is here annexed at once to the _Consensus_. The Consensus, or mutual assent of the parties, is the final and crowning ingredient in the Convention, and it is the special characteristic of agreements falling under one of the four heads of Sale, Partnership, Agency, and Hiring, that, as soon as the assent of the parties has supplied this ingredient, there is _at once_ a Contract. The Consensus draws with it the Obligation, performing, in transactions of the sort specified, the exact functions which are discharged, in the other contracts, by the _Res_ or Thing, by the _Verba_ stipulationis, and by the _Literae_ or written entry in a ledger. Consensual is therefore a term which does not involve the