Philosophical Investigations, reading it together. §49
I'm skipping §48 because it's fairly self-explanatory [no natural way to decide on a simple], but also because the later sections that return to it actually hold the more interesting discussions of the example that it offers. We'll take it up as those discussions crop up.
§49 (and §50!) return to the curious invocation of explanation in the Theaetetus passage quoted in §47. If we recall, there Socrates says that so-called primary elements cannot be explained, insofar as they themselves carry out explanatory work. Explanation is a one-way street, from simples, to composites. However, having 'grammatically relativized' (if we can call it that) what counts as a simple and a composite in §47 and §48, §49 now explores the consequences that this relativization has upon this apparent one-way street.
The consequences are as one would expect: Witty grants that if something counts as a simple in a particular use of langauge, then Socrates is right: the (grammatical) simple cannot be something that describes, insofar as it is only named (names do not describe). However, what are simples in one instance may be complexes in other instances: this is what Witty is getting at when he says that:
§49: "A sign “R” or “B”, etc., may sometimes be a word and sometimes a sentence. But whether it ‘is a word or a sentence’ depends on the situation in which it is uttered or written".
- where 'words' correspond to simples, and 'sentences', to composites. Two examples are given. The first in which someone is trying to describe the complex colored squares of §48 (in order to reconstruct it, say), wherein to speak of "R" is to have "R" function in an explanatory role (An imaginary conversation: Q: "What squares are in positions 1, 2, and 7?"; A: "R"). In this case, "R" describes - it plays an explanatory role. In the second case, one is trying to memorize what exactly is designated (named) by "R" in the first place ("That is 'R'"). In this case, R is not something that explains, but simply names.
One point of interest here is that §49 answers a question posed back in §26, where Witty writes that "One can call [naming] a preparation for the use of a word. But what is it a preparation for?". It's here, in §49, that Witty answers this question: "Naming is a preparation for describing".
As usual, Witty is once again paying close attention to the types of uses of words, without which one can fall into "philosophical superstition", as he calls it here. Such superstitions being, again, the confusion between kinds of uses of words. Here we can see a bit better why such confusions happen: precisely because the role that a word can play is reversible: in one case a simple, in one case a composite, in one case a name, in one case a description - all depending "on the situation in which it is uttered or written".