Data are never free of philosophical encumbrances. Nevertheless, philosophical issues are often considered peripheral to method and evidence. Historical perspectives likewise are not considered integral to most data-driven disputes in contemporary psychological science. This paper examines the history of the investigation of hypnosis over the last 75 years to illuminate how evidence and method are entangled with epistemology and ontology, how new research directions are forged by changes in the cultural and philosophical landscape, and how unacknowledged philosophical assumptions can result (...) in confusion and empirical cul-de-sacs. Theoretical disputes that appear to be simple empirical matters often entail hidden philosophical issues, and apparent historical continuity at the theoretical level can belie discontinuity at the ontological level. The lesson of hypnosis is that philosophical analysis is as important as methodological rigor. 2012 APA, all rights reserved). (shrink)