On Andr\'eka's Conjecture that special relativity is the only possible conceptual reduct of classical kinematics

In this paper, we prove a pure mathematical result which has important implications for the history and philosophy of classical physics and the conceptual origins of relativity theory. In formal terms, we show that, up to definitional equivalence, there is no intermediate model of spacetime lying strictly between special relativity and late classical kinematics. Informally, this means that there was essentially no other option but to switch to special relativity to resolve the conflict between late classical kinematics and the null result of the Michelson--Morley experiment.