“In general, we seem to associate complexity with anything we find difficult to understand.”

1940s, Science and Religion (1941)
Context: It would not be difficult to come to an agreement as to what we understand by science. Science is the century-old endeavor to bring together by means of systematic thought the perceptible phenomena of this world into as thoroughgoing an association as possible. To put it boldly, it is the attempt at the posterior reconstruction of existence by the process of conceptualization. But when asking myself what religion is I cannot think of the answer so easily. And even after finding an answer which may satisfy me at this particular moment, I still remain convinced that I can never under any circumstances bring together, even to a slight extent, the thoughts of all those who have given this question serious consideration.

Music, Mind, and Meaning (1981)

The Internal Constitution of Stars, Cambridge. (1926). ISBN 0521337089
Paraphrased variants: It is sound judgment to hope that in the not too distant future we shall be competent to understand so simple a thing as a star.
It is not too much to hope that in the not too distant future we shall be competent to understand so simple a thing as a star.

W. Brian Arthur in: Mitchell M. Waldrop (2004) Complexity: The Emerging Science at the Edge of Order and Chaos http://books.google.nl/books?id=VP9TWZtVvq8C&pg=PA333. p. 333

Source: A Room with a View (1908), Ch.1

Source: The Road Less Traveled: A New Psychology of Love, Traditional Values, and Spiritual Growth

Letter Eight (12 August 1904)
Letters to a Young Poet (1934)

Source: The Best of Myles (1968)

Source: https://books.google.ru/books/about/%D0%A7%D1%82%D0%BE_%D1%82%D0%BE_%D0%BD%D0%B5%D0%BB%D0%B0%D0%B4%D0%BD%D0%BE%D0%B5.html?id=b-0TEAAAQBAJ&source=kp_book_description&redir_esc=y