In the first part of this paper the author presents physical and philosophical reasons which, in 1905, finally impelled A. Einstein to deny the existence of the ether of 19th century physics, especially H. A. Lorentz's ether. Since Einstein, under the influence of P. Drude, identified Lorentz's ether with absolute space, the denial of Lorentz's ether meant, for Einstein, the denial of the existence of absolute space. The author also presents reasons of the same kind which impelled Einstein, when he was formulating the general relativity, to entirely deny the existence of physical space and time. This denial lasted from 1913 to 1916.
In the second part the author presents physical and philosophical reasons that impelled Einstein in 1916, to again recognise the real existence of space and time and to call them (connected in his theory into one space-time)" the new ether."
