These hypotheses explain and reconcile all the facts: (1) the fact of stellar aberration, because the rays which reach us from the stars are transmitted to us unaltered by the super-ether; (2) the negative result of the Michelson experiment, because the light which we produce in the laboratory travels in the ether that is borne along by the earth, where it originates; (3) the fact that, in spite of the approach or recession of the stars, their light reaches us with the common velocity which it had acquired in the super-ether, shortly after it started. However strange this explanation may seem, it is not absurd, and it raises no insurmountable difficulty. It shows that, if the result of the Michelson experiment is a sort of no-thoroughfare, there are other ways out of it besides Einstein’s theory. To resume the matter, we have offered to us three different ways of escaping the difficulties, the apparent contradictions, involved in our experience—the antinomy arising from aberration and the Michelson result—and they are reduced to these alternatives: 1. The contraction of bodies by velocity is real (Lorentz). 2. The contraction of bodies by velocity is only an appearance due to the laws of the propagation of light (Einstein). 3. The contraction of bodies by velocity is neither real nor apparent: there is no such thing (hypothesis of super-ether connected with ether). This shows that the Einsteinian explanation of phenomena is by no means imposed upon us by the facts, or is at least not absolutely imposed by them to the exclusion of any other explanation. * * * * * Is it at least imposed by reason, by principles, by the evidential character of its rational premises, or because it does not conflict with our good sense and mental habits as the others do? One would suppose this at first, when one compares it with the teaching of Lorentz; and, in order to relieve this discussion, I will for the moment leave out of account the third theory which I sketched, that of a super-ether. What seemed most difficult to admit in Lorentz’s hypothesis of real contraction was that the contraction of bodies was supposed to depend entirely upon their velocity, not in any way upon their nature; that it was supposed to be the same for all bodies, no matter what was their chemical composition or physical condition.