The Historical Necessity of Probability in Quantum Mechanics: A Reassessment of Bohr's Measurement Theory and the Born Rule

This paper reexamines the role of probability in quantum mechanics from a historical and conceptual perspective, focusing on Bohr’s measurement theory and the origin of the Born rule. It argues that probabilistic interpretation did not arise as a mathematical necessity of the wave equation, but as a practical bridge between deterministic wave evolution and discrete measurement outcomes. By distinguishing continuous quantum dynamics from observational statistical rules, the work proposes a layered interpretative framework. The study respects the historical motivations behind complementarity and classical measurement description while clarifying that probability functions primarily at the measurement interface. This perspective aims to provide conceptual clarity and support future reinterpretations of quantum foundations and measurement theory.