What is Brandom's notion of implicitness?

Question

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.

Answer 1

The implicitness that Brandom talks about is implicitness (embeddedness) in bare practice. His idea is that the more basic knowledge is just how to do something. The more advanced knowledge is how to symbolically express what we do. When we achieve that advanced knowledge, what was first implicit in practice, in bare activity, become explicit in that it can be talked about, and reasoned about.

For example, a person may be reasonable, logical, without having any acquaintance with logic. This is the level of bare practice. If that person later learns logic, she will learn how to express in the logical vocabulary what was formerly implicit in her bare actions. The knowledge of logic, in turn, will provide her with additional tools to check for logical validity, when her spontaneous (implicit) logical inclinations might falter.

Answer 2

Just to augment the excellent answer from @Ram Tobolski : for Brandom conceptual content is instituted by normative practice. So our practices can have conceptual content that our languages cannot explicitly express. In fact they always already have such content. This is a brilliant idea that goes a long way in explaining linguistic change. E.g. consider a term like "hook up" in contemporary US. Surely the practice preceeded the term.

so one way to think of implicit v. explicit is as conceptual content instituted by extra-linguistic practice v. the same expressed by linguistic practice.