When two or three legal conceptions are spoken of as anciently blended in one， it is not intended to imply that some one of the included notions may not be older than the others， or， when those other have been formed， may not greatly predominate over and take precedence over them. The reason why one legal conception continues so long to cover several conceptions， and one technical phrase to do instead of several， is doubtless that practical changes are accomplished in the law of primitive societies long before men see occasion to notice or name them. Though I have said that Patriarchal Power was not at first distinguished according to the objects over which it was exercised， I feel sure that Power over Children was the root of the old conception of Power； and I cannot doubt that the earliest use of the Nexum， and the one primarily regarded by those who resorted to it， was to give proper solemnity to the alienation of property. It is likely that a very slight perversion of the Nexum from its original functions first gave rise to its employment in Contracts， and that the very slightness of the change long prevented its being appreciated or noticed. The old name remained because men had not become conscious that they wanted a new one； the old notion clung to the mind because nobody had seen reason to be at the pains of examining it. We have had the process clearly exemplified in the history of Testaments. A Will was at first a simple conveyance of property. It was only the enormous practical difference that gradually showed itself between this particular conveyance and all others which caused it to be regarded separately， and even as it was， centuries elapsed before the ameliorators of law cleared away the useless encumbrance of the nominal mancipation， and consented to care for nothing in the Will but the expressed intentions of the Testator. It is unfortunate that we cannot track the early history of Contracts with the same absolute confidence as the early history of Wills， but we are not quite without hints that contracts first showed themselves through the nexum being put to a new use and afterwards obtained recognition as distinct transactions through the important practical consequences of the experiment. There is some， but not very violent， conjecture in the following delineation of the process. Let us conceive a sale for ready money as the normal type of the Nexum. The seller brought the property of which he intended to dispose —— a slave， for example —— the purchaser attended with the rough ingots of copper which served for money and an indispensable assistant， the libripens， presented himself with a pair of scales. The slave with certain fixed formalities was handed over to the vendee —— the copper was weighed by the libripens and passed to the vendor. So long as the business lasted it was a nexum， and the parties were nexi； but the moment it was completed， the nexum ended， and the vendor and purchaser ceased to bear the name derived from their momentary relation. But now， let us move a step onward in commercial history. Suppose the slave transferred， but the money not paid. In that case， the nexum is finished， so far as the seller is concerned， and when he has once handed over his property， he is no longer nexus； but， in regard to the purchaser， the nexum continues. The transaction， as to his part of it， is incomplete， and he is still considered to be nexus. It follows， therefore， that the same term described the Conveyance by which the right of property was transmitted， and the personal obligation of the debtor for the unpaid purchase-money. We may still go forward， and picture to ourselves a proceeding wholly formal， in which nothing is handed over and nothing paid； we are brought at once to a transaction indicative of much higher commercial activity， an executory Contract of Sale.

　　If it be true that， both in the popular and in the professional view， a Contract was long regarded as an incomplete Conveyance， the truth has importance for many reasons. The speculations of the last century concerning mankind in a state of nature， are not unfairly summed up in the doctrine that “in the primitive society property was nothing， and obligation everything；” and it will now be seen that， if the proposition were revered， it would be nearer the reality. On the other hand， considered historically the primitive association of Conveyances and Contracts explains something which often strikes the scholar and jurist as singularly enigmatical， I mean the extraordinary and uniform severity of very ancient systems of law to debtors， and the extravagant powers which they lodge with creditors. When once we understand that the nexum was artificially prolonged to give time to the debtor， we can better comprehend his position in the eye of the public and of the law. His indebtedness was doubtless regarded as an anomaly， and suspense of payment in general as an artifice and a distortion of strict rule. The person who had duly consummated his part in the transaction must， on the contrary， have stood in peculiar favour； and nothing would seem more natural than to arm him with stringent facilities for enfording the completion of a proceeding which， of strict right， ought never to have been extended or deferred.

　　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.

　　What was an Obligation？ It is defined by the Roman lawyers as “Juris vinculum， quo necessitate adstringimur alicujus solvendae rei.” This definition connects the Obligation with the Nexum through the common metaphor on which they are founded， and shows us with much clearness the pedigree of a peculiar conception. The Obligation is the “bond” or “chain” with which the law joins together persons or groups of persons， in consequence of certain voluntary acts. The acts which have the effect of attracting an Obligation are chiefly those classed under the heads of Contract and Delict， of Agreement and Wrong； but a variety of other acts have a similar consequence which are not capable of being comprised in an exact classification. It is to be remarked， however， that the act does not draw to itself the Obligation in consequence of any moral necessity，。 it is the law which annexes it in the plenitude of its power， a point the more necessary to be noted， because a different doctrine has sometimes been propounded by modern interpreters of the Civil Law who had moral or metaphysical theories of their own to support. The image of a vinculum juris colours and pervades every part of the Roman law of Contract and Delict. The law bound the parties together， and the chain could only be undone by the process called solutio， an expression still figurative， to which our word “payment” is only occasionally and incidentally equivalent. The consistency with which the figurative image was allowed to present itself， explains an otherwise puzzling peculiarity of Roman legal phraseology， the fact that “Obligation” signified rights as well as duties， the right， for example， to have a debt paid as well as the duty of paying it. The Romans kept in fact the entire picture of the “legal chain” before their eyes， and regarded one end of it no more and no less than the other.

　　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 tablebook 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.

　　I have enumerated the four Contracts in their historical order， which order， however， the Roman Institutional writers did not invariably follow. There can be no doubt that the Verbal Contract was the most ancient of the four， and that it is the eldest known descendant of the primitive Nexum. Several species of Verbal Contract were anciently in use， but the most important of all， and the only one treated of by our authorities， was effected by means of a stipulation， that is， a Question and Answer； a question addressed by the person who exacted the promise， and an answer given by the person who made it. This question and answer constituted the additional ingredient which， as I have just explained， was demanded by the primitive notion over and above the mere agreement of the persons interested. They formed the agency by which the Obligation was annexed. The old Nexum has now bequeathed to maturer jurisprudence first of all the conception of a chain uniting the contracting parties， and this has become the Obligation. It has further transmitted the notion of a ceremonial accompanying and consecrating the engagement， and this ceremonial has been transmuted into the Stipulation. The conversion of the solemn conveyance， which was the prominent feature of the original Nexum， into a mere question and answer， would be more of a mystery than it is if we had not the analogous history of Roman Testaments to enlighten us. Looking to that history， we can understand how the formal Conveyance was first separated from the part of the proceeding which had immediate reference to the business in hand， and how afterwards it was omitted altogether. As then the question and answer of the Stipulation were unquestionably the Nexum in a simplified shape， we are prepared to find that they long partook of the nature of a technical form. It would be a mistake to consider them as exclusively recommending themselves to the older Roman Lawyers through their usefulness in furnishing persons meditating an agreement with an opportunity for consideration and reflection. It is not to be disputed that they had a value of this kind， which was gradually recognised； but there is proof that their function in respect to Contracts was at first formal and ceremonial in the statement of our authorities， that not every question and answer was of old sufficient to constitute a Stipulation， but only a question and answer couched in technical phraseology specially appropriated to the particular occasion.

　　But although it is essential for the proper appreciation of the history of contract-law that the Stipulation should be understood to have been looked upon as a solemn form before it was recognised as a useful security， it would be wrong on the other hand to shut our eyes to its real usefulness. The Verbal Contract， though it had lost much of its ancient importance， survived to the latest period of Roman juris prudence； and we may take it for granted that no institution of Roman law had so extended a longevity unless it served some practical advantage. I observe in an English writer some expressions of surprise that the Romans even of the earliest times were content with so meagre a protection against haste and irreflection. But on examining the Stipulation closely， and remembering that we have to do with a state of society in which written evidence was not easily procurable， I think we must admit that this Question and Answer， had it been expressly devised to answer the purpose which it served， would have been justly designated a highly ingenious expedient. It was the promisee who， in the character of stipulator， put all the terms of the contract into the form of a question， and the answer was given by the promisor. “Do you promise that you will deliver me such and such a slave， at such and such a place， on such and such a day？” “I do promise.” Now， if we reflect for a moment， we shall see that this obligation to put the promise interrogatively inverts the natural position of the parties， and， by effectually breaking the tenor of the conversation， prevents the attention from gliding over a dangerous pledge. With us， a verbal promise is， generally speaking， to be gathered exclusively from the words of the promisor. In old Roman law， another step was absolutely required； it was necessary for the promisee， after the agreement had been made， to sum up all its terms in a solemn interrogation； and it was of this interrogation， of course， and of the assent to it， that proof had to be given at the trial —— not of the promise， which was not in itself binding. How great a difference this seemingly insignificant peculiarity may make in the phraseology of contract-law is speedily realised by the beginner in Roman jurisprudence， one of whose first stumbling-blocks is almost universally created by it. When we in English have occasion， in mentioning a contract， to connect it for convenience'' sake with one of the parties —— for example， if we wished to speak generally of a contractor —— it is always the promisor at whom our words are pointing. But the general language of Roman law takes a different turn； it always regards the contract， if we may so speak， from the point of view of the promisee. in Speaking of a party to a contract， it is always the Stipulator， the person who asks the question， who is primarily alluded to. But the serviceableness of the stipulation is most vividly illustrated by referring to the actual examples in the pages of the Latin comic dramatists. If the entire scenes are read down in which these passages occur （ex. gra. Plautus， Pseudolus， Act I. sc. i； Act IV. sc. 6； Trinummus， Act V. sc. 2）， it will be perceived how effectually the attention of the person meditating the promise must have been arrested by the question， and how ample was the opportunity for withdrawal from an improvident undertaking.

　　In the Literal or Written Contract， the formal act， by which an Obligation was superinduced on the Convention， was an entry of the sum due， where it could be specifically ascertained， on the debit side of a ledger. The explanation of this Contract turns on a point or Roman domestic manners， the systematic character and exceeding regularity of bookkeeping in ancient times. There are several minor difficulties of old Roman law， as， for example， the nature of the Slave''s Peculium， which are only cleared up when we recollect that a Roman household consisted or a number of persons strictly accountable to its head， and that every single item of domestic receipt and expenditure， after being entered in waste books， was transferred at stated periods to a general household ledger. There are some obscurities， however， in the descriptions we have received of the Literal Contract， the fact being that the habit of keeping books ceased to be universal in later times， and the expression “Literal Contract” came to signify a form of engagement entirely different from that originally understood. We are not， therefore， in a position to say， with respect to the primitive Literal Contract， whether the obligation was created by a simple entry on the part of the creditor， or whether the consent of the debtor or a corresponding entry in his own books was necessary to give it legal effect. The essential point is however established that， in the case of this Contract， all formalities were dispensed with on a condition being complied with. This is another step downwards in the history of contract-law.

　　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 deliver 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 rounded 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 slightest anomaly， but is exactly analogous to Real， Verbal， and Literal.

　　In the intercourse of life the commonest and most important of all the contracts are unquestionably the four styled Consensual. The larger part of the collective existence of every community is consumed in transactions of buying and selling， of letting and hiring， of alliances between men for purposes of business， of delegation of business from one man to another； and this is no doubt the consideration which led the Romans， as it has led most societies， to relieve these transactions from technical incumbrance， to abstain as much as possible from clogging the most efficient springs of social movement. Such motives were not of course confined to Rome， and the commerce of the Romans with their neighbours must have given them abundant opportunities for observing that the contracts before us tended everywhere to become Consensual， obligatory on the mere signification of mutual assent. Hence， following their usual practice， they distinguished these contracts as contracts Juris Gentium. Yet I do not think that they were so named at a very early period. The first notions of a Jus Gentium may have been deposited in the minds of the Roman lawyers long before the appointment of a Praetor Peregrinus， but it would only be through extensive and regular trade that they would be familiarised with the contractual system of other Italian communities， and such a trade would scarcely attain considerable proportions before Italy had been thoroughly pacified， and the supremacy of Rome conclusively assured. Although， however， there is strong probability that the Consensual Contracts were the latest-born into the Roman system， and though it is likely that the qualification， Juris Gentium， stamps the recency of their origin， yet this very expression， which attributes them to the “Law of Nations，” has in modern times produced the notion of their extreme antiquity. For， when the “Law of Nations” had been converted into the “Law of Nature，” it seemed to be implied that the Consensual Contracts were the type of the agreements most congenial to the natural state； and hence arose the singular belief that the younger the civilisation， the simpler must be its forms of contract.

　　The Consensual Contracts， it will be observed， were extremely limited in number. But it cannot be doubted that they constituted the stage in the history of Contract-law from which all modern conceptions of contract took their start. The motion of the will which constitutes agreement was now completely insulated， and became the subject of separate contemplation； forms were entirely eliminated from the notion of contract， and external acts were only regarded as symbols of the internal act of volition. The Consensual Contracts had， moreover， been classed in the Jus Gentium， and it was not long before this classification drew with it the inference that they were the species of agreement which represented the engagements approved of by Nature and included in her code. This point once reached， we are prepared for several celebrated doctrines and distinctions of the Roman lawyers. One of them is the distinction between Natural and Civil Obligations. When a person of full intellectual maturity had deliberately bound himself by an engagement， he was said to be under a natural obligation， even though he had omitted some necessary formality， and even though through some technical impediment he was devoid of the formal capacity for making a valid contract. The law （and this is what the distinction implies） would not enforce the obligation， but it did not absolutely refuse to recognise it； and natural obligations differed in many respects from obligations which were merely null and void， more particularly in the circumstance that they could be civilly confirmed， if the capacity for contract were subsequently acquired. Another very peculiar doctrine of the jurisconsults could not have had its origin earlier than the period at which the Convention was severed from the technical ingredients of Contract. They taught that though nothing but a Contract could be the foundation of an action， a 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 desig