[eptcyka]

> The internal vs external distinction also maps to other pairs of concepts like synchronous vs asynchronous, pull vs push, direct vs inverted, opaque vs transparent and local vs remote or distributed. This sentence is superfluous, as none of the listed _pairs_ are mentioned anywhere else ever again, besides sync vs async.

[slikts]

It's a major recurring theme; for example, anything that refers to implicit or explicit is part of it. The list you quoted is a placeholder to be elaborated.