At the grand theory level, evidence is represented by practitioners' and scientists' use of the philosophic approaches presented in the theories. As we have sought to build an academic discipline, grand theories have assisted in legitimizing the emerging discipline by providing broad guidelines about the focus of the discipline. There are varying degrees of evidence about the usefulness of existing nursing grand theories. Their frequent use by schools of nursing, care institutions, and practitioners, and their use in guiding research initiatives are examples of their value.