If scientists came up with a device—call it an automatic defrailer—that wouldn’t extend your life but would slash the likelihood you’d end up in a nursing home or miserable with depression, we’d be clamoring for it. We wouldn’t care if doctors had to open up your chest and plug the thing into your heart. We’d have pink-ribbon campaigns to get one for every person over seventy-five. Congress would be holding hearings demanding to know why forty-year-olds couldn’t get them installed. Medical students would be jockeying to become defrailulation specialists, and Wall Street would be bidding up
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