 There is a closely related alternative to this set-up which uses comparative similarity orderings in place of selection functions (D. Lewis 1973; Burgess 1981). Here, an o-frame is a pair \(\langle W, \prec \rangle\) where \(W\) is a non-empty set of possible worlds and \(\prec\) is a ternary relation on the set of worlds, assumed to be transitive and irreflexive relative to its first argument. The relation \(u \prec_w v\) is supposed to mean that world \(u\) is (in some sense) more similar or closer to \(w\) than world \(v\). Let \(R(w) := \{y\in W: \exists z \in W(y\prec_wz)\}\). This corresponds to the set of accessible worlds from \(w\). An o-model is a triple \(\langle W, \prec, V\rangle\) such that \(\langle W, \prec\rangle\) is an o-frame, and \(V\) is a valuation function. We use the abbreviation \(\lvert A\rvert^M_w := \lvert A\rvert^M \cap R(w)\), and let \(min_{\prec_{w}}(U)\) denote the \(U\)-worlds most similar to \(w\) (such that no \(U\)-world is strictly more similar to \(w\)). A simple form of the truth-condition for the variably strict conditional reads as follows: