Einstein Was Not a Flat Physicalist: Principle Theories, Constructive Theories, and the Direction of Constraint

Abstract: Einstein's distinction between principle theories and constructive theories is methodological rather than metaphysical. Principle theories such as thermodynamics and relativity articulate empirically distilled constraints that delimit admissible microphysical models, while constructive theories remain provisional and revisable. This paper reconstructs Einstein's framework from primary sources and argues that recent appeals to it by Meir Hemmo and Orly Shenker (under the banner of "Flat Physicalism") invert its functional hierarchy. What is presented as an Einsteinian template instead supports a reductionist metaphysics foreign to Einstein's methodology and increasingly misaligned with the structural commitments of contemporary physics.