Few weeks went by when he didn&'t receive letters from anxious readers struggling with some attenuated form of failing to recognize old acquaintances. Some were consoled by Weber's bombshell: a simple neurological quirk that revealed how everyone suffered from a form of prosopagnosia. Even normal recognition fails when the observed face is upside down. Mark Schluter was not face-blind. Just the reverse: he saw differences that were not there.