Do Ceteris Paribus Laws Exist? A Regularity-Based Best System Analysis

This paper argues that ceteris paribus (cp) laws exist based on a Lewisian best system analysis of lawhood (BSA). Furthermore, it shows that a BSA faces a second trivialization problem besides the one identified by Lewis. The first point concerns an argument against cp laws by Earman and Roberts. The second point aims to help making some assumptions of the BSA explicit. To address the second trivialization problem, a restriction in terms of natural logical constants is proposed that allows one to describe regularities, as specified by basic generics (e.g. 'birds can fly') and universals (e.g. 'all birds can fly'). It is argued that cp laws rather than strict laws might be a part of the the best system of such a regularity-based BSA, since sets of cp laws can be both (a) simpler and (b) stronger when reconstructed as generic non-material conditionals. Yet, if sets of cp laws might be a part of the best system of a BSA and thus qualify as proper laws of nature, it seems reasonable to conclude that at least some cp laws qualify as proper laws of nature.