“But just like voices, thoughts are underpinned by physical stuff. We know this because alterations to the brain change the kinds of thoughts we can think. In a state of deep sleep, there are no thoughts. When the brain transitions into dream sleep, there are unbidden, bizarre thoughts. During the day we enjoy our normal, well-accepted thoughts, which people enthusiastically modulate by spiking the chemical cocktails of the brain with alcohol, narcotics, cigarettes, coffee, or physical exercise. The state of the physical material determines the state of the thoughts. And the physical material is absolutely necessary for normal thinking to tick along. If you were to injure your pinkie in an accident you’d be distressed, but your conscious experience would be no different. By contrast, if you were to damage an equivalently sized piece of brain tissue, this might change your capacity to understand music, name animals, see colors, judge risk, make decisions, read signals from your body, or understand the concept of a mirror—thereby unmasking the strange, veiled workings of the machinery beneath. Our hopes, dreams, aspirations, fears, comic instincts, great ideas, fetishes, senses of humor, and desires all emerge from this strange organ—and when the brain changes, so do we. So although it’s easy to intuit that thoughts don’t have a physical basis, that they are something like feathers on the wind, they in fact depend directly on the integrity of the enigmatic, three-pound mission control center.”

Source: The Note Book of Elbert Hubbard (1927), p. 64.

Page 75, Consciousness Speaks - Conversations with Ramesh S. Balsekar

Source: Why Zebras Don't Get Ulcers

Knowledge and Global Order https://www.bbvaopenmind.com/en/article/knowledge-and-global-order/?fullscreen=true - OpenMind September 2013

Science and the Unseen World (1929)
Context: However closely we may associate thought with the physical machinery of the brain, the connection is dropped as irrelevant as soon as we consider the fundamental property of thought—that it may be correct or incorrect.... that involves recognising a domain of the other type of law—laws which ought to be kept, but may be broken.<!--V, p.57-58

Source: The Hitchhiker's Guide to the Galaxy

Source: 1970s, The Urgency of Change (1970), p. 184
Context: The brain is the source of thought. The brain is matter and thought is matter. Can the brain — with all its reactions and its immediate responses to every challenge and demand — can the brain be very still? It is not a question of ending thought, but of whether the brain can be completely still? This stillness is not physical death. See what happens when the brain is completely still. <!-- π

As quoted in the article The Human Brain — Three Pounds of Mystery, in 'The Watchtower' magazine (15 July 1978)