Listen. Can you hear an aircraft passing overhead? A dog barking? The twittering of birds? In straining to listen, you have just sent a surge of electrical activity through millions of brain cells. In choosing to do this with your mind, you have changed your brain - you have made brain cells fire, at the side of your head, above the right eye. By the time you've read this far, you will have changed your brain permanently. These words will leave a faint trace in the woven electricity of you. For 'you' exists in the trembling web of connected brain cells. This web is in flux, continually...