The 1970 amended Belgian Constitution is at the cross-roads of two currents of history, on one hand, once more the traditional values of the Occidental society; on the other hand a double communal pressure contests an unitary state: from underneath affirmation of three Belgiannational communities, from above, apparition of a «supra-national party».The authors make a critical examination of the cropping up of bonding institutions in a «pré-fédéral» state, then they clearly state the principles of a really federal Constitution based upon the acknowledgement of the 2 large communities and the 3 regions and the principles of a democratic organization of an economic politic.