When I first meet Vaillant in Boston, he’s dressed in a cheerful blue sweater with holes in it, which seem of a piece with his cheerful, slightly abstracted demeanor. He has dense eyebrows, lively eyes, and an unusually erect bearing for a fellow of seventy-seven. “Your generation can’t imagine a world without attachment,” he tells me as we settle down to chat. “But fancy: before, when behavioral scientists wrote about love, it was all sex.” He’s primarily talking about Freud and Skinner, who couldn’t begin to examine the love between parent and child without seeing eroticism. “They couldn’t
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