It was the express wish of Bahá’u’lláh that after Him the friends should “turn” to ‘Abdu’l‑Bahá. Bahá’u’lláh also said in His Book of Laws that anything that was not clear in His Writings should be “referred” to His Most Mighty Branch springing from the Ancient Root. (See The World Order of Bahá’u’lláh, pages 134–35.) In one of the Tablets of ‘Abdu’l‑Bahá published in Selections from the Writings of ‘Abdu’l‑Bahá (page 214) He quotes the passages mentioned above and interprets them to mean that “whatever He [‘Abdu’l‑Bahá] saith is the very truth.” ‘Abdu’l‑Bahá further says, referring to those who do not accept Him as the Interpreter of the Word of God, “Whoso deviates from my interpretation is a victim of his own fancy” (The World Order of Bahá’u’lláh, page 138). Moreover, in the Star of the West, Volume 12, page 227, ‘Abdu’l‑Bahá interprets the verses from the “Tablet of the Branch” to mean “whatsoever His [‘Abdu’l‑Bahá’s] pen records, that is correct.”1
There is nothing in the Writings that would lead us to the conclusion that what Shoghi Effendi says about himself concerning statements on subjects not directly related to the Faith also applies to ‘Abdu’l‑Bahá. Instead we have assertions which indicate that ‘Abdu’l‑Bahá’s position in the Faith is one for which we find “no parallel” in past Dispensations. For example, Bahá’u’lláh, in addition to His reference to the Center of His Covenant as the “Mystery of God,” states that ‘Abdu’l‑Bahá should be regarded as God’s “exalted Handiwork” and “a Word which God hath adorned with the ornament of His Own Self, and made it sovereign over the earth and all that there is therein.” And from Shoghi Effendi we have the incontrovertible statement that the Guardian of the Faith while “overshadowed” by the “protection” of Bahá’u’lláh and of the Báb, “remains essentially human,” whereas in respect of ‘Abdu’l‑Bahá Shoghi Effendi categorically states that “in the person of ‘Abdu’l‑Bahá the incompatible characteristics of a human nature and superhuman knowledge and perfection have been blended and are completely harmonized.”2
With reference to your question about the “ether,” the various definitions of this word as given in the Oxford English Dictionary all refer to a physical reality, for instance, “an element,” “a substance,” “a medium,” all of which imply a physical and objective reality and, as you say, this was the concept posited by nineteenth century scientists to explain the propagation of light waves. It would have been understood in this sense by the audiences whom ‘Abdu’l‑Bahá was addressing. However, in Chapter XVI of Some Answered Questions, ‘Abdu’l‑Bahá devotes a whole chapter to explaining the difference between things which are “perceptible to the senses” which He calls “objective or sensible,” and realities of the “intellect” which have “no outward form and no place,” and are “not perceptible to the senses.” He gives examples of both “kinds” of “human knowledge.” The first kind is obvious and does not need elaboration. To illustrate the second kind the examples He gives are: love, grief, happiness, the power of the intellect, the human spirit and “ethereal matter.” (In the original Persian the word “ethereal” is the same as “etheric.”) He states clearly that “Even ethereal matter, the forces of which are said in physics to be heat, light, electricity and magnetism, is an intellectual reality, and is not sensible.” In other words, the “ether” is a concept arrived at intellectually to explain certain phenomena. In due course, when scientists failed to confirm the physical existence of the “ether” by delicate experiments, they constructed other intellectual concepts to explain the same phenomena.3
In considering the whole field of divinely conferred “infallibility” one must be careful to avoid the literal understanding and petty-mindedness that has so often characterized discussions of this matter in the Christian world. The Manifestation of God (and, to a lesser degree, ‘Abdu’l‑Bahá and Shoghi Effendi,) has to convey tremendous concepts covering the whole field of human life and activity to people whose present knowledge and degree of understanding are far below His. He must use the limited medium of human language against the limited and often erroneous background of His audience’s traditional knowledge and current understanding to raise them to a wholly new level of awareness and behavior. It is a human tendency, against which the Manifestation warns us, to measure His statements against the inaccurate standard of the acquired knowledge of mankind. We tend to take them and place them within one or other of the existing categories of human philosophy or science while, in reality, they transcend these and will, if properly understood, open new and vast horizons to our understanding.
Some sayings of the Manifestation are clear and obvious. Among these are laws of behavior. Others are elucidations which lead men from their present level of understanding to a new one. Others are pregnant allusions, the significance of which only becomes apparent as the knowledge and understanding of the reader grow. And all are integral parts of one great Revelation intended to raise mankind to a new level of its evolution.
It may well be that we shall find some statement is couched in terms familiar to the audience to which it was first addressed, but is strange now to us. For example, in answer to a question about Bahá’u’lláh’s reference to the “fourth heaven” in the Kitáb-i-Íqán, the Guardian’s secretary wrote on his behalf:
As to the ascent of Christ to the fourth heaven, as revealed in the glorious “Book of Íqán,” he [the Guardian] stated that the “fourth heaven” is a term used and a belief held by the early astronomers. The followers of the Shí‘ih sect likewise held this belief. As the Kitáb-i-Íqán was revealed for the guidance of that sect, this term was used in conformity with the concepts of its followers.
In studying such statements, however, we must have the humility to appreciate the limitations of our own knowledge and outlook, and strive always to understand the purpose of Bahá’u’lláh in making them, trying to look upon Him with His own eyes, as it were.