The Slip-box

Luhmann—the social servant turned sociologist—used the slip-box to reduce the friction of staring at a blank page.

He had two slip-boxes: a bibliographical one, which contained references and brief notes on the literature, and the main one, in which he collected and generated his ideas, mainly in response to what he read.

The main notes that he wrote in response to the bibliographic slip-box were forced to fit on index cards.