How do we lose knowledge about history and science? Black Box focuses on forgotten knowledge through a series of conversations around inexplicable objects and obsolete scientific instruments from the Cabinet of Astronomy and Physics in Kassel. The Cabinet of Astronomy and Physics stores a number of objects with unknown properties. Five of these will be brought from the storage room to the mathematical section of the Cabinet of Astronomy and Physics where, once a week, a set of invited thinkers—artists, philosophers, scientists—meet to wander into the realm of speculation and hypothesis in a homage to the unknown. Just as a black box in an airplane records its journey and technical functioning so that they can be pieced together in the event of an accident, the participants in these talks attempt to piece together the history of the objects under discussion, which are also black boxes in another sense—objects whose function is uncertain. Visitors are welcome to join in the guessing game. The showcase in which these objects are displayed and brought to a new life has been conceived by two artists participating in dOCUMENTA (13), Mariana Castillo Deball and Gabriel Lester. Composed of white boxes, hidden mirrors and multiple perspectives, it exposes the fact that even a single plinth is not a passive structure, but a lens that defines the things we see, and how we see them.