“Luhmann would add the number of one or two (rarely more) notes next to a keyword in the index (Schmidt 2013, 171). The reason he was so economical with notes per keyword and why we too should be very selective lies in the way the slip-box is used. Because it should not be used as an archive, where we just take out what we put in, but as a system to think with, the references between the notes are much more important than the references from the index to a single note. Focusing exclusively on the index would basically mean that we always know upfront what we are looking for”