Others, such as Friedman, has suggested that the field is underdeveloped as a field of science and that it has, consequently, not produced a good scientific understanding of transpersonal phenomena. In his proposal for a new division of labour within the transpersonal field he suggests a distinction between transpersonal studies, a broad category that might include non-scientific approaches, and transpersonal psychology, a more narrow discipline that should align itself more closely with the principles of scientific psychology. However, this criticism has been answered by Ferrer who argues that Friedmans proposal attaches transpersonal psychology to a naturalistic metaphysical worldview that is unsuitable for the domain of spirituality.