In fact, Lewis whole-heartedly accepts that things have accidental properties and, indeed, would accept that (16) is robustly true. His explanation involves one of the most interesting and provocative elements of his theory: the doctrine of counterparts. Roughly, an object y in a world w2 is a counterpart of an object x in w1 if y resembles x and nothing else in w2 resembles x more than y.[19] Each object is thus its own (not necessarily unique) counterpart in the world it inhabits