 Some of the challenges facing the first step will be examined in  Section 5.  The second step too should not be underestimated. Perhaps the greatest worry here is that Boolos’s translation renders expressions from one category (that of monadic predicates) in terms of expressions from another category (that of plural noun phrases). For instance, “… is an apple” is rendered as “the apples”. But these categories are very different  (Section 2).