The essay seems to be predicated on the mistaken notion at the time that the electron has no mass (the proton had not been discovered yet). Of course today philosophers of physics might make similar arguments using gluons; see that other hot thread
https://news.ycombinator.com/item?id=35432918
I found this really fun, reflecting as it does the views before the acceptance and experimental confirmation that there is no lumeniferous aether, and that the speed of light is constant in all reference frames.
I've enjoyed explanations of how Einstein, Planck, and their contemporaries changed our understanding; I've not seen before such a vivid story set in the before times.
What is really funny is that eventually our understanding circled back and now the rest mass of particles is attributed to their interaction with the Higgs field, by effectively the same basic mechanism that Poincare-Lorentz-Abraham invented.
> The aether hypothesis was the topic of considerable debate throughout its history, as it required the existence of an invisible and infinite material with no interaction with physical objects. As the nature of light was explored, especially in the 19th century, the physical qualities required of an aether became increasingly contradictory. By the late 1800s, the existence of the aether was being questioned, although there was no physical theory to replace it.
RIP M Poincare was a great man.