As I have pointed out before, Luhmann considered his Zettelkasten or slip box as his "external memory" and partner in communication with his internal memory. What are some of the advantages of external memory? Recent psychological research strongly suggests that our internal memory does not work like a filing cabinet that can be used simply to retrieve items stored independently of recall. Rather, it seems to rely heavily on "reconstructing" memories. This process is not always reliable. It is also likely to degrade over time, to be influenced by emotional factors, and subject to confusions. External memories, like those kept in a good note-taking system are not subject to such influences. They are "fixed" We can rely on them with more confidence than we can on internal memories.
A similar thing thing holds for the their connections and the further growth based on such connections—or so it seems to me. Internal memories do not support creative interaction with past results in the way in which notes or external memories do.