From Onions to Broccoli: Generalizing Lewis's counterfactual logic
Patrick Girard

Abstract:
We present a generalization of Segerberg?s onion semantics for belief
revision, in which the linearity of the spheres need not occur. The
resulting logic is called broccoli logic. We provide a minimal
relational logic, introducing a new neighborhood semantics
operator. We then show that broccoli logic is a well-known conditional
logic, the Burgess-Veltman minimal conditional logic.