but by 1833 a German physiologist named Johannes Peter Müller (1801–1858) had noticed something puzzling. If he shone light in the eye, put pressure on the eye, or electrically stimulated the nerves of the eye, all of these led to similar sensations of vision—that is, a sensation of light rather than of pressure or electricity. This suggested to him that we are not directly aware of the outside world, but instead only of the signals in the nervous system.8 In other words, when the nervous system tells you that something is “out there”—such as a light—that is what you will believe, irrespective
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