MS 156a
This pocket notebook bears no dates, and, even though a rough dating of this material is possible, there are a few puzzling aspects that cannot be dealt with in a completely satisfactory way.
On the flyleaf, there is a short summary of the contents of this notebook in Wittgenstein’s hand: “Augenbl. Erfahrg. das Reale / Vielleicht / Aesthetik / Bedeutung” (roughly, “Experience of present moment is what’s real / The concept ‘perhaps’ / Aesthetics / Meaning”). As a matter of fact, all four topics listed by Wittgenstein are then treated in the notebook, but the list is by no means complete.
As I said, the question “When was this notebook written?” is not easy to answer. What is obvious is that the first 51 pages (pp. 1r-26r) were in their entirety transferred to TS 219. Here, they form the content of pp. 16-22. However, the date of TS 219 is unknown. It may seem plausible to assume that the entries copied into TS 219 were typed in chronological order, but there is no reason to be very sure about this assumption. If we look at MS 156a itself, it is striking that the handwriting of the first 51 pages is homogeneous and runs on quite smoothly. Presumably, this style of writing is compatible with the idea that these remarks were copied from another source, even if it may seem unlikely that Wittgenstein copied his remarks into a pocket notebook.
However this may be, the first 51 pages must have been written before the typing of TS 219. As the first page plus one remark on p. 2 of this typescript are taken from the last couple of pages of TS 214i, it cannot have been typed before June 1932. So, those 51 pages too must have been written after June 1932. On the other hand, there are a few remarks on later pages of our notebook that were used in the production of MS 114ii (pp. 43-47). So, if we are correct in assuming that the revision (or Umarbeitung) of the BT contained in MS 114ii was written in the late autumn of 1933, we may conjecture that the relevant passages from MS 156a were also written at roughly this time.
As far as I know, this is all the “hard” evidence there is. However, there is some less hard evidence which is difficult to harmonize with the more or less established dating of MS 114ii: there are a number of parallels between remarks following the Umarbeitung-relevant part of MS 156a and Wittgenstein’s lectures in May 1933 (as recorded by Moore, for instance). Of course, the existence of these parallels does not prove that these remarks themselves were written around May 1933. But still, it is worth bearing the fact of the existence of these parallels in mind. If they were really written in May 1933, this may mean that in revising the relevant passages on pp. 43-47 of MS 114ii, Wittgenstein was relying on material composed about half a year earlier.
So, what we can say with confidence is that the entries in the pocket notebook MS 156a were written not earlier than June 1932 and not later than late autumn 1933.