 Thus far this is very like the error theory of J.L. Mackie (Mackie 1946, 1977: ch. 1 and Joyce 2001). But there is a twist. For Mackie, as for Russell, “good” is a meaningful predicate even though there is no property corresponding to the word. But Mackie, unlike Russell, is unfazed by this fact. So far as Mackie is concerned, meaningful predicates that refer to non-existent properties pose no particular problems. But for Russell, we can only talk meaningfully about non-existent things if they are defined in terms of things with which we are acquainted. This is a consequence of his Fundamental Principle that