Roland Barthes wrote that the centre of Tokyo is occupied by a void...it is a quiet forest that lies at Tokyo's heart.
...The centre of Tokyo is certainly a void, but one that is protected by a circular train line, the Yamanote, which forms a 40-km (25-mile) loop around it. It seems to me that this ring of steel emphasizes the importance of the void, and the depth of its significance.
This is the first site along the tour. In here we have a void. I remember the building that used to stand here, it was painted blue. Passing through it, you can imagine how us, as ghosts – should the building be standing here – would have to actually be invisible to pass through these walls and now it’s the reverse. The building is the ghost and we’re passing through these walls.
Japanese music is above all a music of reticence, of atmosphere. When recorded, or amplified by a loudspeaker, the greater part of its charm is lost. In conversation, too, we prefer the soft voice, the understatement. Most important of all are the pauses. Yet the phonograph and radio render these moments of silence utterly lifeless. And so we distort the arts themselves to curry favor for them with the machines.
I'd like to call the more general phenomenon that this is a specific instance of "ghost knowledge": It is knowledge that is present somewhere in the epistemic community, and is perhaps readily accessible to some central member of that community, but it is not really written down anywhere and it's not clear how to access it. Roughly what makes something ghost knowledge is two things:
It is readily discoverable if you have trusted access to expert members of the community.
It is almost completely inaccessible if you are not.
In this sense, most knowledge is ghost, particularly if you take an expansive view of what counts as an epistemic community.