 Lewis  (1983)  argues for the theoretical utility of the notion of naturalness by proposing an array of generalizations linking naturalness to other topics, including similarity, intrinsicness, materialism, laws of nature, and meaning. Subsequent authors have offered competing or complementary proposals. Many proposals, like Lewis’s, purport to “analyse”, or provide necessary and sufficient conditions for, some other property partly in terms of naturalness; some purport to analyse naturalness in terms of other properties; others involve other kinds of generalizations. This section will attempt a survey.