All possess the power of reflection but few use it. When this power is turned outwardly, we look upon the physical body, its organs and senses, as our self and so plunge into the bustling activity of this world without hesitation. But if this same power of reflection be turned inwardly, we begin to forget our activities and to lose knowledge of the physical body and its environment. For we become so deeply indrawn into the world of thought that for the time being this inner world becomes for us the real world. Thus we are led gradually by repeating this practice to identify ourselves with the mind alone, to look upon ourselves as thought-beings.
-- Notebooks Category 4: Elementary Meditation > Chapter 4: Meditative Thinking > # 11