An affirmation that all people are part of a single human family, that a oneness lies buried beneath the manifold diversities and dissensions of the present fragmented world, and that this latent oneness can give life and fire to some programme of social transformation.
This unity means that the constant factors in our genetic heritage and in our upbringing imply similarities in our aspirations and in the process of our lives. While these latter similarities may be somewhat masked by the obvious differences imposed by life in diverse human environments, many features of common humanity stand out above such variations. The phrase also implies that most options available to any member of the human family will become available to any other member.
Alternately, the human commonalities perceived (despite differences of national, ethnic, or racial characteristics, and despite differences of sex, age, physical or mental states, or among economic, political, religious or cultural goals) are conceived, not as some difference-obliterating or ignoring, idealistic unity, but as a federation of different parts of the human family in which, in fact, differentiation plays an important if not crucially essential role in planetary development. This federated unity implies that people may continue to exercise their choices freely so as not to come under any system of 'harmonized' options.
It is everyone's duty, but especially that of Christians, to work with energy for the establishment of universal brotherhood, the indispensable basis for authentic justice and the condition for enduring peace: "We cannot in truthfulness call upon that God who is the Father of all if we refuse to act in a brotherly way toward certain men, created to God's image. A man's relationship with God the Father and his relationship with his brother men are so linked together that Scripture says: 'He who does not love does not know God' (I Jn. 4, 8)". (Papal Writings, 14 May 1971).