<p>Reason (or material) relations of implication and incompatibility hold in virtue of the meanings of linguistic expressions in a given language. As opposed to formal or logical consequence relations, reason relations are often structurally <i>open</i>, i.e., unclosed under principles such as monotonicity or transitivity. In their recent book, Hlobil and Brandom go even further, allowing for such relations to be <i>radically </i>open, i.e., unclosed under any structural principle. In particular, they reject the restrictive forms of monotonicity and transitivity known as cautious monotonicity (CM) and cumulative transitivity (CT). In the present paper, I argue that such radical openness is objectionable on the grounds that it does not allow us to construct for every set even a weak version of Tarski’s notion of a theory, thereby undermining the very notion of consequence. I then lay out minimal principles under which such a construction is possible, and suggest that reason relations should be closed under those principles.</p>