DOUBLE VISION

The mystique of twins.

- PARUL SEHGAL

Half a century later, they still return our gaze, staring back at us in their dark dresses and white stockings, their white headbands pinned in place. The seven-year-old identical twins Cathleen and Colleen Wade stand side by side, pressed together as if to create the illusion that they are conjoined. One twin smiles; the other appraises the photographer. There are remnants of chocolate cake in the creases of their mouths.

Diane Arbus took this portrait, "Identical twins, Roselle, N.J. 1966," at a Christmas party for families of multiples held at a Knights of Columbus hall. She'd been lurking at such events, prospecting for twins and triplets. Through her view-finder, the sisters appear less like two separate children than like split aspects of the same soul, simultaneously innocent and foreboding. "I mean, it resembles them," their father told a reporter at a 2005 retrospective of Arbus's work. "But we've always been baffled that she made them look ghostly. None of the other pictures we have of them looks anything like this."The photograph reportedly inspired Stanley Kubrick's depiction of the eerie sisters in "The Shining." In "How to Be Multiple: The Philosophy of Twins" (Bloomsbury), Helena de Bres aims to rescue twins from the gothic, from horror movies, and from singleton scrutiny, the better to return