Robert Brandom seems to have a very distinct notion of implicitness when he says things like:
For while that vocabulary is not itself descriptive vocabulary, its use is implicit in the use of ordinary descriptive vocabulary. [1]
By "that vocabulary" he is talking about nondescriptive vocabulary that plays a "categorial metalinguistic expressive"[1] role. What I take from this is that he has the idea that there is some vocabulary (nondescriptive), the use of which I already and implicitly know just by knowing how to use some other vocabulary (descriptive). But how am I to understand this very notion of implicitness? Also and very relatedly, what sort of knowledge does he have in mind?
[1] Brandom: From Empiricism to Expressivism, Cambridge: Harvard University Press, 2015, p. 90.
*Note on the source: The ideas at work here must be very similar or identical to those in his Making it explicit, but unfortunately I haven't read it yet.