“Scientific experiences and practices can easily lead to spirituality, rather than trying to memorize more facts.”

The Spiral Staircase: My Climb Out of Darkness (2004)
Context: The one and only test of a valid religious idea, doctrinal statement, spiritual experience, or devotional practice was that it must lead directly to practical compassion. If your understanding of the divine made you kinder, more empathetic, and impelled you to express this sympathy in concrete acts of loving-kindness, this was good theology. But if your notion of God made you unkind, belligerent, cruel, or self-righteous, or if it led you to kill in God's name, it was bad theology. Compassion was the litmus test for the prophets of Israel, for the rabbis of the Talmud, for Jesus, for Paul, and for Muhammad, not to mention Confucius, Lao-tsu, the Buddha, or the sages of the Upanishads.

Source: Memoirs of a Superfluous Man (1943), p. 34
Context: Our preceptors were gentlemen as well as scholars. There was not a grain of sentimentalism in the institution; on the other hand, the place was permeated by a profound sense of justice. … An equalitarian and democratic regime must by consequence assume, tacitly or avowedly, that everybody is educable. The theory of our regime was directly contrary to this. Our preceptors did not see that doctrines of equality and democracy had any footing in the premises. They did not pretend to believe that everyone is educable, for they knew, on the contrary, that very few are educable, very few indeed. They saw this as a fact of nature, like the fact that few are six feet tall. … They accepted the fact that there are practicable ranges of intellectual and spiritual experience which nature has opened to some and closed to others.

Source: Leadership in Administration: A Sociological Interpretation, 1957, p. 48

The Richard Dimbleby Lecture: Science, Delusion and the Appetite for Wonder (1996)

As quoted by George H. W. Bush in remarks while presenting National Medals of Science and Technology http://bushlibrary.tamu.edu/research/papers/1990/90111300.html (13 November 1990). This might be a paraphrase of statements from his introduction to "Science The Endless Frontier" (1945), rather than a direct quote. (see below)

As translated by Alan R. Clarke (1996).
By The River Piedra I Sat Down and Wept (1994)