But to understand the matter fully, we must carefully observe that there are three different ways of speaking, respecting things which ARE, or which, it is supposed, WILL be in our power.
II. The first of these ways is, where an assurance is given of future intentions, and if the assurance be SINCERE at the time it is given, though it should not be carried into effect, no blame is incurred, as it might afterwards not be found expedient. For the human mind has not only a natural power, but a right to change its purpose. Wherefore if any blame attaches to a change of opinion, or purpose, it is not to be imputed to the BARE ACT OF CHANGING, but to the CIRCUMSTANCES, under which it happens, especially when the former resolution was the best.
III. The second way is, when future intentions are expressed by outward acts and signs sufficient to indicate a resolution of abiding by present assurances. And these kind of promises may be called imperfect obligations, but conveying to the person to whom they are given no RIGHT to exact them. For it happens in many cases that we may be under an obligation of duty, to the performance of which another has no right to compel us. For in this respect the duty of fidelity to promises, is like the duties of compassion and gratitude. In such kinds of promises therefore the person to whom they are made, has no right, by the law of nature to possess himself of the effects of the promiser, as his own, nor to COMPEL him to the performance of his promise.
IV. The third way is, where such a determination is confirmed by evident signs of an intention to convey a peculiar right to another, which constitutes the perfect obligation of a promise, and is attended with consequences similar to an alienation of property.
There may be two kinds of alienation, the one of our property, the other of a certain portion of our liberty. Under those of the former kind we may class the promises of gifts, and under the latter the promises of doing certain actions. On this subject we are supplied with noble arguments from the divine oracles, which inform us, that God himself, who can be limited by no established rules of law, would act contrary to his own nature, if he did not perform his promises. From whence it follows that the obligations to perform promises spring from the nature of that unchangeable justice, which is an attribute of God, and common to all who bear his image, in the use of reason. To the proofs of scripture here referred to, we may add the judgment of Solomon, "My son if thou hast been surety for thy friend, thou hast tied up thy hands to a stranger; thou art ensnared by the words of thy mouth, then art thou taken by the words of thine own mouth." Hence a promise is called by the Hebrews a bond or chain, and is compared to a vow. Eustathius in his notes on the second book of the Iliad, assigns a similar origin to the word ὑποσχεσεως {hyposcheseôs} or engagement. For he who has received the promise, in some measure takes and holds the person, that has made the engagement. A meaning not ill expressed by Ovid in the second book of his Metamorphoses, where the promiser says to him, to whom he had promised, "My word has become yours."
After knowing this, there remains no difficulty in replying to the arguments of Connanus. For the expressions of the lawyers, respecting BARE PROMISES, refer only to what was introduced by the Roman laws, which have made a FORMAL STIPULATION the undoubted sign of a deliberate mind.
Nor can it be denied that there were similar laws among other nations. For Seneca, speaking of human laws, and promises made without proper solemnities, says, "What law, of any country, we may add, obliges us to the performance of bare promises?" But there may naturally be other signs of a deliberate mind, besides a formal stipulation, or any other similar act which the civil law requires, to afford grounds for a legal remedy. But what is not done with a deliberate mind, we are inclined to believe does not come under the class of perfect obligations; as Theophrastus has observed in his book on laws. Nay, even what is done with a deliberate mind, but not with an intention of conceding our own right to another; though it cannot give any one a natural right of exacting its fulfilment, yet it creates an obligation not only in point of duty, but in point of moral necessity. The next matter to be considered is, what are the requisites to constitute a perfect promise.
V. The use of reason is the first requisite to constitute the obligation of a promise, which ideots, madmen, and infants are consequently incapable of making. The case of minors is somewhat different. For although they may not have a sound judgment, yet it is not a permanent defect, nor sufficient of itself to invalidate all their acts. It cannot be certainly defined at what period of life reason commences. But it must be judged of from daily actions, or from the particular customs of each country. Amongst the Hebrews a promise made by a male at the age of thirteen, and by a female at the age of twelve, was valid. In other nations, the civil laws, acting upon just motives, declare certain promises made by wards and minors to be void, not only among the Romans, but among the Greeks also, as it has been observed by Dion Chrysostom in his twenty-fifth oration. To do away the effect of improvident promises, some laws introduce actions of recovery, or restitution. But such regulations are peculiar to the civil law, and have no immediate connection with the law of nature and of nations, any farther than that wherever they are established, it is consonant to natural justice that they should be observed. Wherefore if a foreigner enter into an agreement with a citizen or subject of any other country; he will be bound by the laws of that country, to which, during his residence therein, he owes a temporary obedience. But the case is different, where an agreement is made upon the open sea, or in a desert island, or by letters of correspondence. For such contracts are regulated by the law of nature alone, in the same manner as compacts made by sovereigns in their public capacity.
VI. The consideration of promises, made under an error, is a subject of some intricacy. For it, in general, makes a difference, whether the promiser knew the full extent of his promise, and the value of the thing promised, or not, or whether the contract, which was made, originated in fraudulent intention, or not, or whether one of the parties was privy to the fraud; and whether the fulfilment of it was an act of strict justice, or only of good faith. For according to the variety of these circumstances, writers pronounce some acts void and others valid, leaving the injured party a discretionary power to rescind or amend them.
Most of these distinctions originate in the ancient civil, and praetorian Roman law. Though some of them are not strictly founded in reason and truth. But the most obvious and natural way of discovering the truth is by referring to laws, which derive their force and efficacy from the general consent of mankind; so that if a law rests upon the presumption of any fact, which in reality has no existence, such a law is not binding. For when no evidence of the fact can be produced, the entire foundation, on which that law rests must fail. But we must have recourse to the subject, to the words and circumstances of a law, to determine when it is founded on such a presumption.[27]