Measurement

Measurement serves as a central pillar of psychological science, yet it remains a deeply contested concept. This entry traces the historical divergence between physical and psychological measurement traditions, from Maxwell's systematic approach through Stevens' influential redefinition to the statistical path of modern psychometrics, identifying the resulting metrological gap that continues to shape the field. Competing definitions, including metrological, realist, representational, operationalist, pragmatist, and anti-realist, are surveyed alongside recent integrative frameworks that synthesise insights across traditions. The entry examines core debates including the quantity objection, conceptual indeterminacy of psychological attributes, epistemic justification of measurement claims, the role of values and socio-cultural context, and the question of continuity with the natural sciences. Future possibilities are considered, including dynamic and process-oriented measurement, the philosophical challenges posed by artificial intelligence, interdisciplinary connections with other human sciences and metrology, and the ethical and political dimensions of quantifying human attributes.