“Certainly I cannot command the sun to be egg-shaped, nor force your brain to think differently. I cannot see the inside of the sun, nor can I share your private feelings. Yet neither can I change the shape or structure of my own brain, nor have a sensation of it as a contraption like a cauliflower. But if my brain is nonetheless I, the sun is I, the air is I, and society, of which you are a member, is also I—for all these things are just as essential to my existence as my brain.”