Since, in the real contract, each party retains the same property with which he enters and which he at the same time gives up, that which remains identical distinguishes itself, as the property that is in itself present in the contract, from the external things which, in exchange, change their owner. That identical element is the value, in which the objects of the contract, for all the qualitative external diversity of the things, are equal to one another — their universal element (§ 63).

The determination that a laesio enormis annuls the obligation entered into in the contract thus has its source in the concept of contract, and more precisely in the moment that the contracting party, through the alienation of his property, remains an owner, and, in a more precise determination, quantitatively remains the same owner. But the injury is not merely enormous (it is taken to be such when it exceeds half the value), but infinite, when a contract or stipulation for the alienation of an inalienable good (§ 66) has been entered into at all. — A stipulation, moreover, is at first distinguished in its content from the contract in that it signifies some single part or moment of the whole contract, and also in that it is the formal fixing of it, as will be discussed presently. On that side, it contains only the formal determination of the contract — the consent of the one party to perform something, and the consent of the other party to accept it; it has therefore been counted among the so-called unilateral contracts. The distinction of contracts into unilateral and bilateral, as well as other divisions of them in Roman law, are, in part, superficial groupings made on the basis of some single, often external consideration, such as the manner of their formality; in part, they also mix together, among other things, determinations that concern the nature of the contract itself with those that pertain only to legal procedure (actiones) and to the legal effects under positive law, often stemming from wholly external circumstances and doing violence to the concept of right.