The Rosenbach's 50th anniversary exhibition is already open, and the folks in the museum's education department are working on forging connections between the show and the themes of "The Big Nothing." It shouldn't be too hard, since this exhibit, placing items in the museum's enormous collection into 26 alphabetically themed groupings, is most concerned with the spaces in between the objects, the connections that may or may not exist. For example, the "M is for Mistress" category includes the suicide note from Rudolf, crown prince of Austria, found dead with his mistress; a copy of Hawthorne's The Scarlet Letter, starring one of literature's most famous adulterers; and a small journal of unknown origin that contains a handwritten copy of John Donne's "To his mistress, going to bed." The poem is heavily blocked out with ink, and is unreadable without the help of infrared reflectography. This blacked-out page speaks to a particular kind of void, and what nothingness can be used to conceal or censor.

A fascinating addition to the show is the conception of an imaginary dinner party in the dining room. Four people, all with connections to the Rosenbachs but not necessarily to one another -- Alice Liddell Hargreaves (as in Alice in Wonderland), Einstein, FDR and Houdini -- are represented through artifacts and themed materials (a tea set marked with playing cards near Hargreaves' seat, for example), to re-create an evening that never took place. In this silent space lies the possibilities of dozens of conversations, stories and anecdotes, many made clear through the museum's notes on the installation, others left for the viewer's imagination.

Through Aug. 15, The Rosenbach Museum and Library, 2008-2010 Delancey Place, 215-732-1600.