The Only Tradition examines the first principles of the perennial philosophy or ancient wisdom tradition as expressed in the writings of René Guénon and Ananda K. Coomaraswamy, and the current breakdown of value, meaning, and culture in the West due to the decline of these principles since the thirteenth century. The book further focuses on the relationship or reciprocity between the first principles and Western and Eastern culture, and discusses the future development of a homogenous, worldwide system of belief that would restore value and meaning to people's lives.

Quinn argues for a return to the first principles inherent in the perennial philosophy, which constitute the sacred primordial Tradition and which inform all the world's great religious traditions. His book makes an excellent introduction to this powerful current of European esoteric thought—primordial tradition.