The mirror, you might say, was an early personal technology -- ingenious, portable, effective -- and like all such technologies, it changed its users. By giving us, for the first time, a readily available image of ourselves that matched what others saw, it encouraged self-consciousness and introspection and, as some worried, excesses of vanity.

In a rebuke to Karl Marx, we have not become the alienated slaves of the machine; we have made the machines more like us and in the process toppled decades of criticism about the dangerous and potentially enervating effects of our technologies.