In The Spirit of Psychotherapy, Holmes considers whether the principles which underpin religion this can be applied to the largely secular world of psychotherapy.

Having a belief system is generally associated with good physical and mental health, and the prime focus of psychotherapy theory and practice is intrapersonal and interpersonal, but these are nested in an often-unexamined supra-personal context, sociological, ecological and spiritual. Structured around a qualitative study based on in-depth interviews with people from a wide range of faith backgrounds, Holmes presents the role belief and spirituality play in everyday lives. From these interviews the author identifies core themes such as attachment and hope; frameworks of meaning and rhythm and ritual. Individual chapters are devoted to detailed descriptions of subjects' accounts of these, while drawing parallels and implications for psychotherapy.