This work is an ambitious, original, and searching study as to what constitutes and comprises ‘mental health’. It advances the proposition that existential or holistic health depends on integral wholeness, the synthesis of body, mind, and heart. As such, a tri-dimensional model is proposed based on the triadic self, rooted in philosophical perspectives on the subject, arguing throughout that the human person is a unity-in-diversity, that one is always whole and well in one’s Self (essence), which must be distinguished from the ego (personality). The importance and relevance of the Enneagram as a foundational system for understanding human personality is referenced throughout. The various strands and thought-threads in the book coalesce around the central doctrine of nonduality exemplified by mystical Christianity and the philosophia perennis.