The Principle of Oneness ...

Let there be no mistake. The principle of the Oneness of Mankind – the pivot round which all the teachings of Bahá'u'lláh revolve – is no mere outburst of ignorant emotionalism or an expression of vague and pious hope. Its appeal is not to be merely identified with a reawakening of the spirit of brotherhood and goodwill among men, nor does it aim solely at the fostering of harmonious co-operation among individual peoples and nations. Its implications are deeper, its claims greater than any which the Prophets of old were allowed to advance. Its message is applicable not only to the individual, but concerns itself primarily with the nature of those essential relationships that must bind all the states and nations as members of one human family. It does not constitute merely the enunciation of an ideal, but stands inseparably associated with an institution adequate to embody its truth, demonstrate its validity, and perpetuate its influence. It implies an organic change in the structure of present-day society, a change such as the world has not yet experienced. It constitutes a challenge, at once bold and universal, to outworn shibboleths of national creeds–creeds that have had their day and which must, in the ordinary course of events as shaped and controlled by Providence, give way to a new gospel, fundamentally different from, and infinitely superior to, what the world has already conceived. It calls for no less than the reconstruction and the demilitarization of the whole civilized world–a world organically unified in all the essential aspects of its life, its political machinery, its spiritual aspiration, its trade and finance, its script and language, and yet infinite in the diversity of the national characteristics of its federated units. ...

 The principle of the Oneness of Mankind, as proclaimed by Bahá'u'lláh, carries with it no more and no less than a solemn assertion that attainment to this final stage in this stupendous evolution is not only necessary but inevitable ...

Shoghi Effendi, The World Order of Bahá’u’lláh