Eckhart Tolle argues that thoughts aren't physical objects a brain surgeon could find. They're invisible energy that exists in memory banks we can't see, separate from the electrical activity neurons produce.
Chapters
But what is a thought? What is its nature? Could you identify a thought by cutting open the brain, your brain? Brain surgeon cuts open your thought. Could he find a thought? No, he sees the activity of neurons. But what is all the stuff that you carry in your memory banks, so to speak, that does not exist on the level of visibility? You cannot find it. It already exists in the realm of the invisible. All the things that in your— all hundreds of thousands, million memories that you carry that you could access at any moment. How does that live in you? So thought is a mystery, but we can experience it and we can see that undoubtedly it is an invisible energy form.