The semantics for counterfactuals due to David Lewis has been challenged on
the basis of unlikely, or impossible, events. Such events may skew a given
similarity order in favour of those possible worlds which exhibit them. By
updating the relational structure of a model according to a ceteris paribus
clause one forces out, in a natural manner, those possible worlds which do not
satisfy the requirements of the clause. We develop a ceteris paribus logic for
counterfactual reasoning capable of performing such actions, and offer several
alternative (relaxed) interpretations of ceteris paribus. We apply this
framework in a way which allows us to reason counterfactually without having
our similarity order skewed by unlikely events. This continues the
investigation of formal ceteris paribus reasoning, which has previously been
applied to preferences, logics of game forms, and questions in decision-making,
among other areas.Comment: In Proceedings TARK 2015, arXiv:1606.0729