“[in Italian Renaissance] there was no 'subject-matter'. What we call subject matter now, was then painting itself. Subject matter came later on when parts of those works were taken out arbitrarily, when a man for no reason is sitting, standing or lying down. He became a bather, she became a bather; she was reclining; he just stood there looking ahead. That is when the posing in painting began… For really, when you think of all the life and death problems in the art of Renaissance, who cares if a Chevalier is laughing or that a young girl has a red blouse on.”

Source: Zen and the Art of Motorcycle Maintenance (1974), Ch. 29
Context: What is essential to understand at this point is that until now there was no such thing as mind and matter, subject and object, form and substance. Those divisions are just dialectical inventions that came later. The modern mind sometimes tends to balk at the thought of these dichotomies being inventions and says, "Well, the divisions were there for the Greeks to discover," and you have to say, "Where were they? Point to them!" And the modern mind gets a little confused and wonders what this is all about anyway, and still believes the divisions were there.
But they weren't, as Phædrus said. They are just ghosts, immortal gods of the modern mythos which appear to us to be real because we are in that mythos. But in reality they are just as much an artistic creation as the anthropomorphic Gods they replaced.

1974
1970's, interview, K. Horsfield & L. Blumenthal

The Notebooks of Leonardo da Vinci (1883), IX The Practice of Painting
Context: When you wish to represent a man speaking to a number of people, consider the matter of which he has to treat and adapt his action to the subject. Thus, if he speaks persuasively, let his action be appropriate to it. If the matter in hand be to set forth an argument, let the speaker, with the fingers of the right hand hold one finger of the left hand, having the two smaller ones closed; and his face alert, and turned towards the people with mouth a little open, to look as though he spoke; and if he is sitting let him appear as though about to rise, with his head forward. If you represent him standing make him leaning slightly forward with body and head towards the people. These you must represent as silent and attentive, all looking at the orator's face with gestures of admiration; and make some old men in astonishment at the things they hear, with the corners of their mouths pulled down and drawn in, their cheeks full of furrows, and their eyebrows raised, and wrinkling the forehead where they meet.

Source: I'd Tell You I Love You, But Then I'd Have to Kill You

In an interview (March 1960) with David Sylvester, edited for broadcasting by the BBC first published in ‘Living Arts, June 1963; as quoted in Interviews with American Artists, by David Sylvester; Chatto & Windus, London 2001, p. 31
1960s

“It was good work,” I said.
“It was hack work. Huge, loud, demanding, popular, but ultimately soulless. Just because it came from the heart didn’t make it good.”
Zima Blue (p. 395)
Short fiction, Zima Blue and Other Stories (2006)

Fifteen Americans, Exhibition catalogue, Museum of Modern Art, 1952 p. 12
1950s

Joint statement with Adolph Gottlieb, to Edwin A. Jewell, often referred to as a Manifesto. (written 7 June 1943; published 13 June 1943)
1940's

Introduction
Cosmic Imagery: Key Images in the History of Science (2008)
Context: Mathematics became an experimental subject. Individuals could follow previously intractable problems by simply watching what happened when they were programmed into a personal computer.... The PC revolution has made science more visual and more immediate.... by creating films of imaginary experiences of mathematical worlds.... Words are no longer enough.