The notion of «the common good», which is crucial for understanding humankind and society, is not immediately obvious. It is, moreover, widely understood and used according to meanings that are irreconcilable and internally contradictory. The essay, after distinguishing between a notional exposition and the possibility of analysing the common good as the constitutive profile of human reality, deepens the structure and sense of order of life in association. This order, inasmuch as it takes shape and consistency through the free and (...) generous cooperation among individuals, may be described as the integrating moment of the common good, the nucleus of society inasmuch as expression of the original social reality of humanity. The common good is constituted through the participation of individuals and - together, circularly and progressively - opens itself up as the place of their possible realization. In this way the common good is the inescapable key to understanding the mystery of our social and historical condition. (shrink)