The jacket text of the British first edition explains:[1] The Perennial Philosophy is an attempt to present this Highest Common Factor of all theologies by assembling passages from the writings of those saints and prophets who have approached a direct spiritual knowledge of the Divine...[1]The book offers readers, who are assumed to be familiar with the Christian religion and the Bible, a fresh approach employing Eastern and Western mysticism: Mr. Huxley quotes from the Chinese Taoist philosophers, from followers of Buddha and Mohammed, from the Brahmin scriptures and from Christian mystics ranging from St John of the Cross to William Law, giving preference to those whose writings, often illuminated by genius, are unfamiliar to the modern reader.

[1]The final paragraph of the jacket text states: In this profoundly important work, Mr. Huxley has made no attempt to 'found a new religion'; but in analyzing the Natural Theology of the Saints, as he has described it, he provides us with an absolute standard of faith by which we can judge both our moral depravity as individuals and the insane and often criminal behaviour of the national societies we have created.

[2]Huxley chose less well-known quotations because "familiarity with traditionally hallowed writings tends to breed, not indeed contempt, but ... a kind of reverential insensibility, ... an inward deafness to the meaning of the sacred words.

"[6] Similarly, forty years later Huston Smith, a religious scholar, wrote that, in The Perennial Philosophy: Huxley provides us with the most systematic statement of his mature outlook.

Chad Walsh, writing in the Journal of Bible and Religion[8] in 1948, spoke of Huxley's distinguished family background, only to continue: The only startling fact, and the one that could not have been predicted by the most discerning sociologist or psychologist, is that in his mid-forties he was destined to turn also to mysticism, and that since his conversion he was to be one of a small group in California busily writing books to win as many people as possible over to the "perennial philosophy" as a way of life.

C. E. M. Joad wrote in New Statesman and Society that, although the book was a mine of learning and Huxley's commentary was profound, readers would be surprised to find that he had adopted a series of peculiar beliefs such as the curative power of relics and spiritual presences incarnated in sacramental objects.

Finally, Joad asserted that Huxley's mistake was in his "intellectual whole-hoggery" and that he was led by ideas untempered by ordinary human experience.

[11] Huxley's Introduction to The Perennial Philosophy begins: The metaphysic that recognises a divine Reality substantial to the world of things and lives and minds; the psychology that finds in the soul something similar to, or even identical with, divine Reality; the ethic that places man's final end in the knowledge of the immanent and transcendent Ground of all being — the thing is immemorial and universal.

Rudiments of the Perennial Philosophy may be found among the traditionary lore of primitive peoples in every region of the world, and in its fully developed forms it has a place in every one of the higher religions.

A version of this Highest Common Factor in all preceding and subsequent theologies was first committed to writing more than twenty-five centuries ago, and since that time the inexhaustible theme has been treated again and again, from the standpoint of every religious tradition and in all the principal languages of Asia and Europe.