And in 1910[A 24] and 1912[A 25] Einstein explained that he borrowed the principle of the constancy of light from Lorentz's immobile ether, but he recognized that this principle together with the principle of relativity makes the ether useless and leads to special relativity.It is curious that anyone would question such an innocuous statement since it is footnoted with Einstein's own words. Furthermore, why would anyone doubt that a scientist relied on the prior published and famous work of another scientist?
The answer is that historians and philosophers adamantly maintain that Einstein's 1905 relativity paper was a wholly original paradigm shift that did not depend on any previous theory or experiment.
A German Einstein scholar answered with his own translations:
Read the 1912 paper (Relativity and Gravitation: Reply to a Comment by M. Abraham, translation in Einstein's Collected papers, vol. 4). Einstein wrote:You can read more about how Einstein's relativity was based on earlier work by Lorentz and Poincare in my book, How Einstein Ruined Physics.
English "...it is impossible to base a theory of the transformation laws of space and time on the principle of relativity alone. As we know, this is connected with the relativity of the concepts of “simultaneity” and “shape of moving bodies.” To fill this gap, I introduced the principle of the constancy of the velocity of light, which I borrowed from H. A. Lorentz’s theory of the stationary luminiferous ether, and which, like the principle of relativity, contains a physical assumption that seemed to be justified only by the relevant experiments (experiments by Fizeau, Rowland, etc.). " German: "Es ist allgemein bekannt, dass auf das Relativitätsprinzip allein eine Theorie der Transformationsgesetze von Raum und Zeit nicht gegründet werden kann. Es hängt dies bekanntlich mit der Relativität der Begriffe „Gleichzeitigkeit“ und „Gestalt bewegter Körper“ zusammen. Um diese Lücke auszufüllen, führte ich das der H. A. Lorentzschen Theorie des ruhenden Lichtäthers entlehnte Prinzip der Konstanz der Lichtgeschwindigkeit ein, das ebenso wie das Relativitätsprinzip eine physikalische Voraussetzung enthält, die nur durch die einschlägigen Erfahrungen gerechtfertigt erschien (Versuche von Fizeau, Rowland usw.)"Or the 1909 paper:English: "According to Lorentz's theory, if a light beam propagates through space, it does so with a speed c in the resting frame K of the ether, independently of the state of motion of the emitting object. Let's call this the constancy of the speed of light principle." German: "Pflanzt sich nämlich ein Lichtstrahl im Vakuum fort, so geschieht dies nach der LORENTZschen Theorie in bezug auf ein im Äther ruhendes Koordinatensystem K stets mit der bestimmten Geschwindigkeit c, unabhängig vom Bewegungszustande des emittierenden Körpers. Wir wollen diesen Satz das Prinzip von der Konstanz der Lichtgeschwindigkeit nennen."See also the link you gave (http://www.aip.org/history/einstein/essay-einstein-relativity.htm):
The second of Einstein's principles is based on an important consequence of Maxwell's laws of electricity, magnetism, and optics, as interpreted by H. A. Lorentz near the end of the nineteenth century.
As you can see, Einstein acknowledged in the above papers getting his famous two relativity postulates from Lorentz. Sometimes Einstein's originality is claimed to be in formulating Lorentz's theory in terms of postulates, but Einstein got the postulates from Lorentz also.
My book accuses Einstein of insufficiently crediting Lorentz and Poincare, so perhaps the above quotes should have been included. But the book does say that in the several years after 1905, relativity was sometimes called the "Lorentz-Einstein theory", and Einstein himself used that term in papers. It was widely known that Einstein got his main ideas from Lorentz's papers, and no one could deny it. My criticism of Einstein is that he failed to describe his sources in his famous 1905 relativity paper, and after he got famous, he claimed sole credit for relativity in dozens of speeches, interviews, and writings for the rest of his life.