 The most obvious similarity between the two sets of definitions is that each seeks to provide for the elimination of what purport to be semantically complex referring expressions. The most obvious difference consists in the fact that Wittgenstein’s definitions are designed to eliminate not definite descriptions, but rather terms for complexes, for example the expression “[aRb],” which, judging by remarks in the Notebooks, is to be read: “a in the relation R to b” (NB, 48) (This gloss seems to derive from Russell’s manner of speaking of complexes in Principia Mathematica, where examples of terms for complexes include, in addition to “a in the relation R to b,” “a having the quality q”, and “a and b and c standing in the relation S” (PM, 44).). One might wonder why this difference should exist. That is to say, one might wonder why Wittgenstein does not treat the peculiar locution “a in the relation R to b” as a definite description — say, “the complex consisting of a and b, combined so that aRb”? This description could then be eliminated by applying the Tractatus’s own variant upon the theory of descriptions: 