 It is easy to get enough of a feel for what is going on in this table to the point where one could confidently say, for many other such pairs, which would be better to put in Column 1 and which in the Column 2. This article is concerned with a semi-technical use of the word ‘natural’ which can be illustrated by these examples: in each case, the property in the Column 1 is more natural than the corresponding property in the Column 2. This use has deep historical roots (see  §2),  but was cemented in a seminal paper by David Lewis  (1983),  and has subsequently been taken up by many other authors.