By means of this article we tried to develop the theoretical basis of contract qualification, regarded as the authentic math of dynamic civil relations. Thus, our scientific approach is built on the idea that the complexity of human interactions inevitably is reveled in the content of a certain contract entity. This juridical construction usually retains some specific elements that justify a more difficult perception of the will of the parties. In this situation the main priority of the legal adviser or even the judge needs to regard the particular direction of the contract will to the realization of a proper cause, which is the key to understanding the specific interest of any subject of contract relations.