Physicists of the nineteenth and early twentieth centuries believed in an undetectable substance called ether- one that supposedly pervaded all space, defining its extent and acting as a medium for light and other electromagnetic waveforms. 'Abdul- Baha challenged this concept, denying that ether has any objective physical existence. It should be regarded- He said- rather as an intellectual abstraction. This position was later vindicated by Einstein as a key insight of his theory of relativity. The crude, mechanical ether of yesteryear is replaced in modern theory by a quasi- mathematical framework physicists call the 'fabric' of the space- time continuum. Although most scientists (with notable exceptions such as Jeans and Eddington) decline to use the old- fashioned name, this radically redefined ether is an entity whose characteristics precisely match those affirmed by 'Abdul- Baha.