There is now a significant literature on the effects of Brexit for the differentiated forms of integration that have become an increasingly familiar feature of the EU's political landscape. While the significance of British withdrawal for questions of differentiation is not difficult to establish, there is little agreement in the literature on whether Brexit will lead to a more or less differentiated EU, which aspects of withdrawal are most relevant, and how the specified causal mechanisms operate. This article takes stock of the debate, discussing four distinct causal pathways: (1) the removal of the UK's opt-outs; (2) the lessons of the British experience; (3) Brexit as a catalyst for reform; and (4) the future UK-EU relationship. The article suggests a more starkly differentiated EU post-Brexit is likely precluded by the political context of disintegration, which downplays negative lessons, reinforces EU unity, and disincentives a 'British model' of external differentiation.