Fichte says that the duty of performing an agreement arises when one party thereto begins to act under it. Juristically this seems to be a rationalization of the Roman innominate contract. There, in case a pact was performed on one side, he who performed might claim restitution _quasi ex contractu_ or claim the counter-performance _ex contractu_. Philosophically the idea seems to be that of the equivalent theory, in the form with which we are familiar in Anglo-American discussion of this subject as the injurious-reliance theory. According to the latter, unless the promisee has parted with an equivalent or has begun to act in reliance upon the agreement, he has no moral claim to fulfilment. This is not a theory of the law as it is or as it ever has been. Formal contracts require nothing of the sort. It is true, English equity, under the influence of the equivalent theory, did lay down in the nineteenth century that a contract under seal with no common-law consideration behind it would not be enforced. But that proposition was subject to many exceptions when it was announced, more have since developed and more are developing. As things are, the exceptions are of more frequent application than the rule itself. Nor is Fichte's theory a statement of moral ideas of his day or of ours. Then and now the moral duty to keep abstract promises was and is recognized. That a man's word should be "as good as his bond" expresses the moral sentiment of civilized society. But the philosopher saw that the law did not go so far and was trying to frame a rational explanation of why it fell short. It should be noticed that Fichte is really trying to show why a promise may be regarded as a part of one's substance and why one's claim to performance may be treated as his property. Hegel also explains contract in terms of property, treating a promise as a disposition of one's substance. Hence in his view the so-called abstract promise is a mere subjective qualification of one's will which he is at liberty to change. This theory and the foregoing assume the Roman law or the older law of Continental Europe, and speak from the reaction from natural law which in England at the same time was overruling the liberal doctrines of Lord Mansfield.