This was entitled "2 Women" by the Boston Public Library, but our analysis finds that it's a single ghost that is bilocating.  Photo by Leslie Jones, date uncertain.

An encounter with one's own ghost, date uncertain.

From the Costică Acsinte Archive.

"Architecture doubles as atmosphere" (Interiors magazine, 1968).  This accidental double exposure is from C. W. Allen's WWII album, scanned by the San Diego Air and Space Museum Archive.

Here's a Portuguese sand castle courtesy of a double exposure, as scanned by the Biblioteca de Arte / Art Library Fundação Calouste Gulbenkian.

You've heard that a person has a light side and a shadow side.  However, "you must remember that you have two light sides instead of just one" (Popular Science, Sept. 1941).  Our photographic proof is from a 1939 yearbook scanned by Miami University Libraries.

Two plates stuck together, from the Australian National Maritime Museum’s William Hall collection.

"Do we see ourselves in others?  Do we look back from outside and see ourselves?  Do we see growth and expansion?  Do we see our greater self?" (James Anderson Charleson, Experience Personal Fulfillment, 2013).  Our photo of someone seeing her greater self in another is an "overlay of images of Amadeo and Lucie (Portugal, 1915)."