The combinatory logic analogue of Rice's theorem says that there is no complete nontrivial predicate. A "predicate" is a combinator that, when applied, returns either T or F. A predicate N is "nontrivial" if there are two arguments "A" and "B" such that N "A" = T and N "B" = F. A combinator N is "complete" if and only if N"M" has a normal form for every argument "M". The analogue of Rice's theorem then says that every complete predicate is trivial. The proof of this theorem is rather simple.