Later metaphysical jurists rely upon the idea of personality. The Romanist thinks of a legal transaction as a willing of some change in a person's sphere of rights to which the law, carrying out his will, gives the intended effect. If the transaction is executed, revocation would involve aggression upon the substance of another. If it is executory, however, why should the declared intent that the change take place in the future be executed by law despite the altered will of the promisor? Some say that this should be done where there is a joint will from which only joint action may recede. Where the parties have come to an agreement, where their wills have been at one, the law is to give effect to this joint will as a sort of vindication of personality. It is evident, however, that this explanation assumes the will theory, the subjective theory of legal transactions. If we start from the objective theory it breaks down. Take for instance the case of an offer, which a reasonable man would understand in a given way, accepted by the offeree in that understanding when the offerer really meant something else. Or take the case of an offer wrongly transmitted by telegraph and accepted in good faith as it is transmitted. Here there is no community of will and yet the law may well hold, as we do in America, in both cases, that there is a contract. No metaphysical theory has prevailed to prevent the steady march of the law and of juristic thought in the direction of an objective doctrine of legal transactions. Nowhere, indeed, has the deductive method broken down so completely as in the attempt to deduce principles upon which contracts are to be enforced. Later in the nineteenth century men came to think more about freedom of contract than about enforcement of promises when made. To Spencer and the mechanical positivists, conceiving of law negatively as a system of hands off while men do things, rather than as a system of ordering to prevent friction and waste so that they may do things, the important institution was a right of free exchange and free contract, deduced from the law of equal freedom as a sort of freedom of economic motion and locomotion. Justice required that each individual be at liberty to make free use of his natural powers in bargains and exchanges and promises except as he interfered with like action on the part of his fellow men, or with some other of their natural rights. Whether all such transactions should be enforced against him or only some, and if the latter, which, are questions belonging to an affirmative rather than to a negative science of law.