Have you ever sat very quietly with closed eyes and watched the movement of your own thinking? Have you watched your mind working? or rather, has your mind watched itself in operation, just to see what your thoughts are, what your feelings are, how you look at the trees, at the flowers, at the birds, at people, how you respond to a suggestion or react to a new idea? Have you ever done this?

Think on these things (ed. HarperCollins Publishers, 1970)