(Sektion 137: Philosophische Untersuchungen von Ludwig Wittgenstein).
This section includes a brief introduction to the problem of rule-following that will be made explicit in the next few sections--agreed by most historians of philosophy to be one of the most interesting problems and discussions in the entire Philosophische Untersuchungen. Wittgenstein is led to the discussion of rules from his consideration of fitting (passen), when do, for example, certain predicates fit (or apply to) the subjects they supposedly describe. When, and why, does it fit a proposition to say that it is true or false, for example? This leads Wittgenstein to a more general question about fitting: why does an object in a series fit in with the rest of a series? For example, a letter in the alphabet follows another letter (L follows K). But why does L fit into the series in this way? In what does the fitting consist? (This is analagous (Wittgenstein is famous for his analogies) to asking: "in what does the fitting of truth to a proposition consist"? Why does the question, in the case of the alphabet, seems so strange?)
137. How is it then, if we determine the subject of a proposition by means of the question "Who or what . . . .?"--Here there is surely something that 'fits' the subject of this question; for otherwise how should we find out what the subject was by means of the question? We find it as much as we find which letter of the alphabet comes after 'K' by saying the alphabet up to 'K'. In what sense does only 'L' fit this series of letters?--In that sense "one could also say "true" and "false" fit propositions; and one could say children learn to differentiate propositions from other expressions by means of one saying to them: "Ask yourself whether you can say 'is true' after it. If these words fit, it is thus a proposition." (And in the same way one could have said: Ask yourself whether you can put the words "This is how things are:" in front of it.)