“The universe as we know it is a joint product of the observer and the observed.”

Book I, Chapter 4, "What Lies behind the Law"
Mere Christianity (1952)

De Abaitua interview (1998)

observes it
Source: 1980s, Notes on an epistemology for living things, 1981, p.258

The Artful Universe (1995)
Context: Where there is life there is a pattern, and where there is a pattern there is mathematics. Once that germ of rationality and order exists to turn a chaos into a cosmos, then so does mathematics. There could not be a non-mathematical Universe containing living observers.<!-- Ch. 5, p. 230

5th Public Talk Saanen (26th July 1970); also in "Fear and Pleasure", The Collected Works, Vol. X
1970s
Context: Do you decide to observe? Or do you merely observe? Do you decide and say, "I am going to observe and learn"? For then there is the question: "Who is deciding?" Is it will that says, "I must"? And when it fails, it chastises itself further and says, "I must, must, must"; in that there is conflict; therefore the state of mind that has decided to observe is not observation at all. You are walking down the road, somebody passes you by, you observe and you may say to yourself, "How ugly he is; how he smells; I wish he would not do this or that". You are aware of your responses to that passer-by, you are aware that you are judging, condemning or justifying; you are observing. You do not say, "I must not judge, I must not justify". In being aware of your responses, there is no decision at all. You see somebody who insulted you yesterday. Immediately all your hackles are up, you become nervous or anxious, you begin to dislike; be aware of your dislike, be aware of all that, do not "decide" to be aware. Observe, and in that observation there is neither the "observer" nor the "observed" — there is only observation taking place. The "observer" exists only when you accumulate in the observation; when you say, "He is my friend because he has flattered me", or, "He is not my friend, because he has said something ugly about me, or something true which I do not like." That is accumulation through observation and that accumulation is the observer. When you observe without accumulation, then there is no judgement.

Sir Hermann Bondi, "Review of Cosmology," Monthly Notices of the Royal Astronomical Society 1948, p. 107-8, as cited in: Hermann Friedmann. Wissenschaft und Symbol, Biederstein, 1949, p. 472

Hazel's Dad, p. 213-214
The Fault in Our Stars (2012)

“Our Nation, A Product of Christianity,” Springfield Republican, 1884, editorial.
1880s