“An open society such as ours is based on the recognition that our understanding of reality is inherently imperfect. Nobody is in possession of the ultimate truth. As the philosopher Karl Popper has shown, the ultimate truth is not attainable even in science. All theories are subject to testing and the process of replacing old theories with better ones never ends.”

Source: What Is This Thing Called Science? (Third Edition; 1999), Chapter 6, Sophisticated falsification, novel predictions and the growth of science, p. 83

The Beginning of Time (1996)

Commenting upon the Aleinu prayer, in "Why We Remain Jews" (1962)
Context: The kingdom is Yours, and You will reign in glory for all eternity. As it is written in Your Torah: "The Lord shall reign for ever and ever." And it is said: " And the Lord shall be King over all the earth: on that day the Lord shall be One, and His name One."
No nobler dream was ever dreamt. It is surely nobler to be a victim of the most noble dream than to profit from a sordid reality and to wallow in it. Dream is akin to aspiration. And aspiration is a kind of divination of an enigmatic vision. And an enigmatic vision in the emphatic sense is the perception of the ultimate mystery, of the truth of the ultimate mystery. The truth of the ultimate mystery — the truth that there is an ultimate mystery, that being is radically mysterious — cannot be denied even by the unbelieving Jew of our age. That unbelieving Jew of our age, if he has any education, is ordinarily a positivist, a believer in Science, if not a positivist without any education.

Pt. I, ch. 1, sec. 2.
1920s, Process and Reality: An Essay in Cosmology (1929)
Context: In all philosophic theory there is an ultimate which is actual in virtue of its accidents. It is only then capable of characterization through its accidental embodiments, and apart from these accidents is devoid of actuality. In the philosophy of organism this ultimate is termed creativity; and God] is its primordial, non-temporal accident. In [[monistic philosophies, Spinoza's or absolute idealism, this ultimate is God, who is also equivalently termed The Absolute. In such monistic schemes, the ultimate is illegitimately allowed a final, eminent reality, beyond that ascribed to any of its accidents. In this general position the philosophy of organism seems to approximate more to some strains of Indian, or Chinese, thought, than to western Asiatic, or European, thought. One side makes process ultimate; the other side makes fact ultimate.

As quoted in An Indian pilgrim: an unfinished autobiography (1997) by himself, Sisir Kumar Bose, and Sugata Bose, p. 124
Context: Reality is, after all, too big for our frail understanding to fully comprehend. Nevertheless, we have to build our life on the theory which contains the maximum truth. We cannot sit still because we cannot, or do not, know the Absolute Truth.

Conjectures and Refutations: The Growth of Scientific Knowledge (1963)

Greater than Sky, Vaster than Space, (2018), Part I

Pt. II, ch. 10, sec. 1.
1920s, Process and Reality: An Essay in Cosmology (1929)

[The Cosmic Landscape: String Theory and the Illusion of Intelligent Design, 2008, Little, Brown, https://books.google.com/books?id=RIW9E1sOyxUC&q=epitome#v=snippet&q=epitome&f=false]