Niels Bohr: Physicist-Philosopher in Action

Niels Bohr was one of the central figures in the emergence of quantum mechanics and a paradigmatic example of a scientist who engaged reflectively with his own practice. For several decades, he was also a leading voice in the philosophical interpretation of the theory. Yet toward the end of the twentieth century his influence declined sharply, and his views came to be widely dismissed as obscure or irrelevant. To evaluate Bohr's contributions, we need to resist the analytic philosopher's urge to separate ontology from action---to treat questions about what there is as detachable from the concrete practices through which physical descriptions are articulated and assessed. That ontology-first stance fits uneasily with Bohr's philosophical sensibility, shaped by a Danish tradition that emphasized reflection on meaning, practice, and responsibility rather than the construction of autonomous metaphysical systems. Seen from this perspective, Bohr's philosophical project comes into focus: his central concern was not the limits of knowledge, but with how our concepts can be extended unambiguously into new domains.