“The second doctrine of the Perennial Philosophy — that it is possible to know the Divine Ground by a direct intuition higher than discursive reasoning — is to be found in all the great religions of the world. A philosopher who is content merely to know about the ultimate Reality — theoretically and by hearsay — is compared by Buddha to a herdsman of other men’s cows. Mohammed uses an even homelier barnyard metaphor. For him the philosopher who has not realized his metaphysics is just an ass bearing a load of books. Christian, Hindu, Taoist teachers wrote no less emphatically about the absurd pretensions of mere learning and analytic reasoning.”

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

Source: Lectures on the Will to Know (1970), pp. 4-5

The Difference Between the Democritean and Epicurean Philosophy of Nature (1841)

The Tragic Sense of Life (1913), VI : In the Depths of the Abyss

Indian Spirituality and Life (1919)

Against the Galilaeans (c. 362)
Context: All of us, without being taught, have attained to a belief in some sort of divinity, though it is not easy for all men to know the precise truth about it, nor is it possible for those who do know it to tell it to all men. … Surely, besides this conception which is common to all men, there is another also. I mean that we are all by nature so closely dependent on the heavens and the gods that are visible therein, that even if any man conceives of another god besides these, he in every case assigns to him the heavens as his dwelling-place; not that he thereby separates him from the earth, but he so to speak establishes the King of the All in the heavens as in the most honourable place of all, and conceives of him as overseeing from there the affairs of this world. What need have I to summon Hellenes and Hebrews as witnesses of this? There exists no man who does not stretch out his hands towards the heavens when he prays; and whether he swears by one god or several, if he has any notion at all of the divine, he turns heavenward. And it was very natural that men should feel thus.

As quoted in Nava-Vēda : God and Man (Nara and Narayan) (1968‎) by M. B. Raja Rao, p. 229

The Usurpation Of Language (1910)
Context: We want philosophers, among other reasons, because the world is full of false philosophy. The way of experience is beset on every hand by a multitude of verbal judgments, of empty phrases, of word-copies, which pass themselves off as the real thing, which pretend to do duty for concrete fact and, by force of their number and importunity, capture our attention and cause the true originals to be overlooked. If it is true that philosophy must perforce fight its battles with words, is it not equally true that words are the weapons against which it must everywhere contend? The philosopher bent on the enlargement of experience perceives at once that his work cannot be done, cannot even be commenced, until he has cleared away the heaps of verbal detritus under which the bedrocks of experience lie buried.

Source: The Cambridge Companion to Newton, 2002, p. 1