As our window onto the world, and onto ourselves, a popular medium molds what we see and how we see it — and eventually, if we use it enough, it changes who we are, as individuals and as a society. “The effects of technology do not occur at the level of opinions or concepts,” wrote McLuhan. Rather, they alter “patterns of perception steadily and without any resistance.” The showman exaggerates to make his point, but the point stands. Media work their magic, or their mischief, on the nervous system itself.