IIRC, Robert Pirsig (author of Zen and the Art of Motorcycle Maintenance) described pretty much exactly this method of taking and organising notes on index cards in Lila, his 1991 follow-up to Zen ....
Does anyone know whether Pirsig got the idea from Luhmann, Luhmann from Pirsig, both from someone else, or if both invented it independently?
hah that was my first thought as well; I've always been tempted to try it, but I was dubious about whether I'd have the discipline to keep the cards organized, and I feared that if I tried to make myself a piece of software to do it that I'd get so distracted by writing the software that I'd never write any notes. So I'm curious to give it a whirl now with someone else's software :)
At least Luhmann was trained in German public administration after the Second World War. The general ideas or seeds for his invention of the Zettelkasten stem from there.
Does anyone know whether Pirsig got the idea from Luhmann, Luhmann from Pirsig, both from someone else, or if both invented it independently?