Convergences and Divergences: Einstein, Poincar\'e, and Special Relativity

Abstract

Jean-Marc Ginoux's recent book, "Poincar\'e, Einstein and the Discovery of Special Relativity: An End to the Controversy" (2024), seeks to close the debate over the respective roles of Poincar\'e and Einstein. Yet what is presented as an "end" may instead invite a more careful analysis of how similar equations can conceal divergent conceptions. The aim here is not to rehearse priority disputes but to show how Einstein's ether-free, principle-based kinematics marked out a path that, unlike its contemporaries, became the canonical form of special relativity. To this end, I reconstruct side by side the 1905 derivations of Poincar\'e and Einstein, tracing their similarities and, more importantly, their differences. This paper reconstructs, in a novel way, the 1905 derivations of Einstein and Poincar\'e, highlighting their contrasting paths.