James Vafiadis

Quantum mechanics reconfigures classical assumptions about objectivity by showing that physical description cannot be separated from the processes through which phenomena become intelligible. While Niels Bohr is often read as an instrumentalist or cautious anti-realist, this paper argues instead that his account of measurement advances a transcendental analysis of the conditions under which physical properties can count as objective at all. On this reading, complementarity is not a limit on access to an underlying reality, but a constraint on the forms of description through which physical properties become determinate and communicable. Drawing on a neo-Kantian perspective, I argue that objectivity in quantum theory is neither representational nor observer-independent but is realised through participatory conditions that anchor physical meaning within shared spatio-temporal and causal frameworks. The slogan ‘to be is to measure’ is defended as shorthand for the claim that objective physical properties are not revealed as pre-existing features of nature but arise only within experimental contexts that disclose them as intelligible objects within a shared mode of possible experience.

Ernst Cassirer's Determinism and Indeterminism in Modern Physics (DI; Cassirer, 1936/1956) constitutes a major but systematically overlooked transformation in the philosophy of quantum mechanics. Against interpretations that treat the text as a late application of his earlier structuralism, this article argues that quantum mechanics forces a fundamental reconstruction of causal order and scientific objectivity. Following the dissolution of Laplacean determinism, causality is no longer directed at ‘things’ in the world, but functions as a regulative demand that experience be rendered intelligible. Accordingly, causal order does not map to a pre-given reality but is progressively constituted from within experience through recursive processes of functional co-ordination (Zuordnung). This reconstruction culminates in a participatory account of objectivity organised through three mutually conditioning levels – measurements, laws, and principles. The upshot is that physical objects emerge as invariant nodes within relational structure; objects are fixed as objective relations. On this basis, the article shows that neither epistemic nor ontic structural realism adequately captures Cassirer's position and develops in response a provisional functional ontology in which a co-ordinating subject and an indeterminate relational domain jointly constitute the transcendental conditions of objectivity. The article concludes by situating DI within a broader participatory tradition in the foundations of physics, arguing that Cassirer's recursive and observer-dependent account of objectivity anticipates key developments in second-order cybernetics and participatory approaches to quantum mechanics.