“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.”

“Western Civ,” p. 19.
Giants and Dwarfs (1990)
Context: I am now even more persuaded of the urgent need to study why Socrates was accused. The dislike of philosophy is perennial, and the seeds of the condemnation of Socrates are present at all times, not in the bosoms of pleasure-seekers, who don’t give a damn, but in those of high-minded and idealistic persons who do not want to submit their aspirations to examination.

Introduction to the Bhagavad-Gita (1944)

Introduction to the Bhagavad-Gita (1944)
Context: The Bhagavad-Gita is perhaps the most systematic scriptural statement of the Perennial Philosophy. To a world at war, a world that, because it lacks the intellectual and spiritual prerequisites to peace, can only hope to patch up some kind of precarious armed truce, it stands pointing, clearly and unmistakably, to the only road of escape from the self-imposed necessity of self-destruction.

Introduction to the Bhagavad-Gita (1944)
Context: 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.

Introduction to the Bhagavad-Gita (1944)
Context: 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.

First Speech on the Conciliation with America (1774)

Indian Spirituality and Life (1919)
Context: The fundamental idea of all Indian religion is one common to the highest human thinking everywhere. The supreme truth of all that is is a Being or an existence beyond the mental and physical appearances we contact here. Beyond mind, life and body there is a Spirit and Self containing all that is finite and infinite, surpassing all that is relative, a supreme Absolute, originating and supporting all that is transient, a one Eternal. A one transcendent, universal, original and sempiternal Divinity or divine Essence, Consciousness, Force and Bliss is the fount and continent and inhabitant of things.
Soul, nature, life are only a manifestation or partial phenomenon of this self-aware Eternity and this conscious Eternal.

Sermon at Hackney Unitarian Church, London, on 24th April 1870.

Robert Elsmere. Book iv. Chap. xxvi, reported in Bartlett's Familiar Quotations, 10th ed. (1919).