In Mind and World John McDowell is worried:
How can we stand up for the constraints placed on our knowledge by "the way things are" without either falling for a Davidson-style coherentism (where beliefs can be justified only by other beliefs, not by some kind of epistemic relation to something extra-mental) or a Given (shown specious by Sellars)? Davidson's willingness to accomodate (through coherence) the Kantian spontaneity of concept-making that we all share raises for McDowell "the spectre of a frictionless spinning in a void." (MW 18) Instead, McDowell writes, "We seem to need rational constraints on thinking and judging, from a reality external to them, if we are to make sense of them as bearing on a reality outside thought at all." (MW 25) Where, I wonder does this need come from? It's not a practical need, surely; it's more of an architectonic need, a need that systems require. But since the explicit ambition of the system McDowell is pressing for is to connect with "the world" it seems odd to use the word "need" in connection with the solution to his concern.