Within the scientific study of spirituality there are substantial ambiguities and uncertainties about relevant concepts, terms, evidences, methods, and relationships. Different disciplinary approaches reveal or emphasize different aspects of spirituality, such as outcomes, behaviors, skills, ambitions, and beliefs. I argue that these aspects interdepend in a way that constitutes a “systems model of spirituality.” This model enables a more holistic understanding of the nature of spirituality, and suggests a new definition that disambiguates spirituality from related concepts such as religion, cultural (...) sophistication, and prosocial behavior in animals. It also exposes important open questions about the nature of spirituality. To support the emerging scientific approach to the study of spirituality, I propose the development of a “philosophy of spirituality” that can clarify the conceptual terrain, identify important research directions, and facilitate a comprehensive and interdisciplinary investigation into the nature, validity, and implications of spirituality's conceptual and practical entailments. (shrink)