According to the thesis, equality between shareholders is a functional and incomplete concept, whatever its importance and relativity. The implementation of this principle meet both a need for "protection", which requires the shareholders' interests to be taken into consideration in the framework of the structures of the firm, and for "direction", namely to ensure the efficacy of financial markets and the success of Belgian limited companies. To demonstrate this, the thesis deepen the intrinsic relativity of the principle of equality, avail an original perception of economic law and clarify the founding principles of equality between shareholders, before making a distinction between "internal" and "external" equality of shareholders and dealing with some issues of "equilibrium" (the "equality of speech" of the shareholders and the social responsability of the firm).