Pius XII on the Unity of Humanity

In the light of this unity of all mankind, which exists in law and in fact, individuals do not feel themselves isolated units, like grains of sand, but united by the very force of their nature and by their internal destiny, into an organic, harmonious mutual relationship which varies with the changing of times.

And the nations, despite a difference of development due to diverse conditions of life and of culture, are not destined to break the unity of the human race, but rather to enrich and embellish it by the sharing of their own peculiar gifts and by that reciprocal interchange of goods which can be possible and efficacious only when a mutual love and a lively sense of charity unite all the sons of the same Father and all those redeemed by the same Divine Blood.