At the core of the Perennial Philosophy we find four fundamental doctrines.
First: the phenomenal world of matter and of individualized consciousness — the world of things and animals and men and even gods — is the manifestation of a Divine Ground within which all partial realities have their being, and apart from which they would be non-existent.
Second: human beings are capable not merely of knowing about the Divine Ground by inference; they can also realize its existence by a direct intuition, superior to discursive reasoning. This immediate knowledge unites the knower with that which is known.
Third: man possesses a double nature, a phenomenal ego and an eternal Self, which is the inner man, the spirit, the spark of divinity within the soul. It is possible for a man, if he so desires, to identify himself with the spirit and therefore with the Divine Ground, which is of the same or like nature with the spirit.
Fourth: man's life on earth has only one end and purpose: to identify himself with his eternal Self and so to come to unitive knowledge of the Divine Ground.

More than twenty-five centuries have passed since that which has been called the Perennial Philosophy was first committed to writing; and in the course of those centuries it has found expression, now partial, now complete, now in this form, now in that, again and again. In Vedanta and Hebrew prophecy, in the Tao Teh King and the Platonic dialogues, in the Gospel according to St. John and Mahayana theology, in Plotinus and the Areopagite, among the Persian Sufis and the Christian mystics of the Middle Ages and the Renaissance — the Perennial Philosophy has spoken almost all the languages of Asia and Europe and has made use of the terminology and traditions of every one of the higher religions. But under all this confusion of tongues and myths, of local histories and particularist doctrines, there remains a Highest Common Factor, which is the Perennial Philosophy in what may be called its chemically pure state. This final purity can never, of course, be expressed by any verbal statement of the philosophy, however undogmatic that statement may be, however deliberately syncretistic. The very fact that it is set down at a certain time by a certain writer, using this or that language, automatically imposes a certain sociological and personal bias on the doctrines so formulated. It is only in the act of contemplation when words and even personality are transcended, that the pure state of the Perennial Philosophy can actually be known. The records left by those who have known it in this way make it abundantly clear that all of them, whether Hindu, Buddhist, Hebrew, Taoist, Christian, or Mohammedan, were attempting to describe the same essentially indescribable Fact.

I have tried to show that the Perennial Philosophy and its ethical corollaries constitute a Highest Common Factor, present in all the major religions of the world. To affirm this truth has never been more imperatively necessary than at the present time. There will never be enduring peace unless and until human beings come to accept a philosophy of life more adequate to the cosmic and psychological facts than the insane idolatries of nationalism and the advertising man's apocalyptic faith in Progress towards a mechanized New Jerusalem. All the elements of this philosophy are present, as we have seen, in the traditional religions. But in existing circumstances there is not the slightest chance that any of the traditional religions will obtain universal acceptance. Europeans and Americans will see no reason for being converted to Hinduism, say, or Buddhism. And the people of Asia can hardly be expected to renounce their own traditions for the Christianity professed, often sincerely, by the imperialists who, for four hundred years and more, have been systematically attacking, exploiting, and oppressing, and are now trying to finish off the work of destruction by “educating” them. But happily there is the Highest Common Factor of all religions, the Perennial Philosophy which has always and everywhere been the metaphysical system of prophets, saints and sages. It is perfectly possible for people to remain good Christians, Hindus, Buddhists, or Moslems and yet to be united in full agreement on the basic doctrines of the Perennial Philosophy.

To the exponents of the Perennial Philosophy, the question whether Progress is inevitable or even real is not a matter of primary importance. For them, the important thing is that individual men and women should come to the unitive knowledge of the divine Ground, and what interests them in regard to the social environment is not its progressiveness or non-progressiveness (whatever those terms may mean), but the degree to which it helps or hinders individuals in the their advance towards man's final end.

Discussing the problem concretely, he finds that both in its spirit and deeper conceptualization, the Perennial Philosophy is opposed to and is also opposed by the so-called "revealed religions" which make salvation and God's truth dependent on a unique and single revelation in history, dependent on an authorized mediator, and makes it a privilege of a particular church or ummah. Perennial Philosophy recognizes no such historical fatality, no priviledged intermediaries, no surrogates, no authorized proxies. Spiritual life is a lawful process, not a lucky accident or piece of history, a happenstance. Salvation is man's assussured possession, not a chance windfall. God is not a pie in the sky who appeared from nowhere at a particular time and became operative in human affairs; he has been active from the beginning. The great spiritual life resides in the heart and its truths are open to all sincere seekers. Man has known, possessed and lived those truths long before "revealed religions" were heard of.

Ancient philosophies were entranced by the order of the cosmos; they marveled at the mysterious power that kept the heavenly bodies in their orbits and the seas within bounds and that ensured that the earth regularly came to life again after the dearth of winter, and they longed to participate in this richer and more permanent existence. They expressed this yearning in terms of what is known as the perennial philosophy, so called because it was present, in some form, in most premodern cultures.11 Every single person, object, or experience was seen as a replica, a pale shadow, of a reality that was stronger and more enduring than anything in their ordinary experience but that they only glimpsed in visionary moments or in dreams. By ritually imitating what they understood to be the gestures and actions of their celestial alter egos — whether gods, ancestors, or culture heroes — premodern folk felt themselves to be caught up in their larger dimension of being.

The content of the universal and primordial doctrine is the following, expressed in Vedantic terms: "Brahma is Reality; the world is appearance; the soul is not other than Brahma". These are the three great theses of integral metaphysics; one positive, one negative, one unitive.

This Indian doctrine declares human cognition of the entire manifold universe to be illusionary in character. The vast multitude of tangible objects and tangible creatures, which we so plainly witness around us were said to be the product of the constructive imagination of the One Hidden Self. Man and his material environments were but finite dreams passing through the mind of the Infinite Dreamer. Consequently all that we know of the world is nothing more or less than a series of idea held in our consciousness. Thus we arrive at a completely idealistic metaphysics, which because of its very nature, must apparently remain forever purely speculative and beyond the scope of the finest instruments, which can be devised to prove or disprove. Nevertheless the strangeness and unfamiliarity of the doctrine fascinated the Indian mind to an amazing extent. That this early foreshadowing of modem idealistic philosophy was not merely a worthless superstition is evidenced by the fact that some brilliant minds of the West have been equally fascinated and perplexed."

A divine philosopher is he who through ascetic purification and noetic contemplation has achieved a direct union with God, and is a true friend of God, in that he esteems and loves the supreme, creative and true wisdom above every other love, wisdom and knowledge.

this is the last word of Western and Eastern wisdom alike. The Hindu Upanishads say: He who thinks that God is not comprehended, by him God is comprehended; but he who thinks that God is comprehended knows him not. God is unknown to those who know him, and is known to those who do not know him at all. Goethe says it in words which, to the modern mind, may be plainer: The highest to which man can attain is wonder; and if the prime phenomenon makes him wonder, let him be content; nothing higher can it give him, and nothing further should he seek for behind it; here is the limit.

One cannot state too clearly that a doctrinal formulation is perfect, not because it exhausts the infinite Truth on the plane of logic, which is impossible, but because it realizes a mental form capable of communicating, to whoever is intellectually apt to receive it, a ray of that Truth, and thereby a virtuality of the total Truth. This explains why the traditional doctrines are always apparently naive, at least from the point of view of philosophers − that is to say, of men who do not understand that the goal and sufficient reason of wisdom do not lie on the plane of its formal affirmation; and that, by definition, there is no common measure and no continuity between thought, whose operations have no more than a symbolic value, and pure Truth, which is identical with That which "is" and thereby includes him who thinks.