The German sociologist Niklas Luhmann, who was famous for his “slip box” or “zettelkästen” method, called his box of notecards his conversation partner. He made each note card as if someone else were going to read it. Because, he would point out, by the time he came to a card a couple days/weeks/months later, he would be someone else.

The note card should be able to communicate a complete thought or idea or story or lesson that an ignorant audience (me) can understand, learn from, or be surprised by.

“One of the most basic presuppositions of communication,” Luhmann writes, “is that the partners can mutually surprise each other.”