Another of ‘Abdu’l-Bahá’s principles is that of the oneness of mankind. All that ‘Abdu’l-Bahá expressed through utterance or action He expressed from the positive and steadfast realization that mankind, in its origin and its end, is one spiritual Man, whose atoms, so to speak, we are. Today, as we see and feel the immediate inter-action of events and conditions throughout the world, and how no portion of humanity is independent of any other portion, we begin to realize something of the significance of this Bahá’í teaching. Thus for the first time one undeviating standard is available for the guidance of religions, governments, industries, education, science and art alike, and that standard is the promotion of the oneness of mankind. Whatever promotes unity is of the universal cause, and will prove fruitful and enduring; but whatever prevents unity is of limited effect, and will be rejected by the Holy Spirit whose action is predominant over all.

Another principle expressed by ‘Abdu’l-Bahá is that the foundation of all religion is one. For by “foundation” ‘Abdu’l-Bahá means the manifestation of the Holy Spirit, from which all the religions originally came. The Holy Spirit is at all times one, though like the spring season it comes and goes, for the Holy Spirit is the expression of the will of God, and God is not divided against Himself, but the people of the world are divided. It is this division of the people which causes differences in the effects of the Holy Spirit from age to age, for the Holy Spirit is perfect and complete in itself, but enters the world of humanity only according to the capacity of the time. It is an inexhaustible ocean, while the people are but small vessels that quickly overflow. Thus Moses, Buddha, Christ, Muḥammad seem different beings and founders of different religions; we see them in the mirror of the world’s division and not in the light of the Holy Spirit. In that light they are one being, one essence, one cause, one power and one foundation; and whatever they uttered is the reality, which we have seized and divided (interpreted) for our own gain, as the soldiers seized and divided the garments of Jesus. ‘Abdu’l-Bahá has said that when representatives of all the world’s religions have gathered for a sincere investigation of the foundation of religion, their oneness will become manifest and all the secondary, man-made features of religion will utterly disappear.

A fourth principle which ‘Abdu’l-Bahá enunciated was that religion must be in accord with science and reason. Now a person who is sick is limited by that sickness both physically and mentally, and he himself cannot overcome those limitations except by attaining health. In the same way there are limitations which fall upon the understanding from sickness of soul. It is spiritual sickness which makes it possible for a man to cling to a religion at variance with science and reason. He may not realize these limitations, but that is part of the disease. These limitations shut out the ray of the spirit, as a wall shuts out the sun. Thus irrational religion does not and cannot become truly predominant in human affairs. Even the fanatic does not follow out his religion in all things, but his self-interest or self-gratification is served in devious ways. Without the Holy Spirit a religion cannot awaken souls, but irrational religion gains influence over material affairs through being itself material.