But if this be true, it has more important bearings than simply to enlarge the definition of the word promise.  It concerns the theory of contract.  The consequences of a binding promise at common law are not affected by the degree of power which the promisor possesses over the promised event.  If the promised event does not come to pass, the plaintiff’s property is sold to satisfy the damages, within certain limits, which the promisee has suffered by the failure.  The consequences are the same in kind whether the promise is that it shall rain, or that another man shall paint a picture, or that the promisor will deliver a bale of cotton.

[300] If the legal consequence is the same in all cases, it seems proper that all contracts should be considered from the same legal point of view.  In the case of a binding promise that it shall rain to-morrow, the immediate legal effect of what the promisor does is, that he takes the risk of the event, within certain defined limits, as between himself and the promisee.  He does no more when he promises to deliver a bale of cotton.

If it be proper to state the common-law meaning of promise and contract in this way, it has the advantage of freeing the subject from the superfluous theory that contract is a qualified subjection of one will to another, a kind of limited slavery.  It might be so regarded if the law compelled men to perform their contracts, or if it allowed promisees to exercise such compulsion.  If, when a man promised to labor for another, the law made him do it, his relation to his promisee might be called a servitude ad hoc with some truth.  But that is what the law never does.  It never interferes until a promise has been broken, and therefore cannot possibly be performed according to its tenor.  It is true that in some instances equity does what is called compelling specific performance.  But, in the first place, I am speaking of the common law, and, in the next, this only means that equity compels the performance of certain elements of the total promise which are still capable of performance.  For instance, take a promise to convey land within a certain time, a court of equity is not in the habit of interfering until the time has gone by, so that the promise cannot be performed as made.  But if the conveyance is more important than the time, and the promisee prefers to have it late rather than never, the law may compel the performance of [301] that.  Not literally compel even in that case, however, but put the promisor in prison unless he will convey.  This remedy is an exceptional one.  The only universal consequence of a legally binding promise is, that the law makes the promisor pay damages if the promised event does not come to pass.  In every case it leaves him free from interference until the time for fulfilment has gone by, and therefore free to break his contract if he chooses.