"Grasping a Thought" (or a sense) is a sort of "primitive" in Frege's philosophy; it is a basic assumption that is not analyzed further.
Frege says that thoughts are real ("wirklich") because they act on the mind, like a physical object acts on the eye. The act of "seeing" performed by the eye is the (visual) perception of the object; in a similar way, we may say that the act of "grasping" performed by the mind is the (mental) understanding of the thought (or sense).
It can be frustrating ... bu Frege has no "theory of mind", nor a thpoery of language aquisition.
A corresponding primitive in his thought is reference ("Bedeutung") and in the same way Frege does not explain how the relation of denotation (i.e. the relation between a name and an object) works.
Only some philosophers may think that we lear it "by ostension"...
Regarding "the picture theory of meaning that the later Frege rejected", we have to consider the fundamental Context principle that Frege formulated already in 1884 and that is present also in Wittgenstein's TLP.
There is a discussion of TLP in the Frege-Wittgenstein correspondence [1918-1919; see: Burton Dreben and Juliet Floyd, Frege-Wittgenstein Correspondence, into : Enzo De Pellegrin (editor), Interactive Wittgenstein : Essays in Memory of Georg Henrik von Wright (2011), with a reference by Frege in a footnote to Der Gedanke], but it seems to me that there is no discussion of this topic.
Von Wright became aware of the special beauty of some of Wittgenstein’s remarks when he stayed at Cornell University as a guest of Norman Malcolm. The two men first met at Cambridge in 1939, but they became friends only when attending Wittgenstein’s very last lecture in 1947 (Von Wright 1992b: 215, 1995b). Immediately after Wittgenstein’s death, they began what would develop into a lifelong friendship cultivated through regular visits and written correspondence. Having resigned from his chair at Cambridge 1 year after Wittgenstein’s death, and fearing that his home country, Finland, which he had moved back to, could be incorporated into the Soviet Union, von Wright proposed that Malcolm should act in his place as literary executor, if he ended up being isolated from the West:
As you probably know, Ludwig Wittgenstein in his will gave to Rhees, Miss Anscombe and me the copyright in his unpublished writings with the wish that we shall publish as many of them as we think fit.
Should it now – for some reason or other – happen that the other executors will not be able to consult and contact me about the editing and publication of the manuscripts, I should like them to consult you and you to exercise the same authority as regards their publication as I possess according to the will. I completely trust your judgment in the matters concerned, and I know that Wittgenstein would have done so too. 5
This was probably as much a measure to ensure continued work on Wittgenstein’s writings as it was an expression of trust. It might also have signalled that von Wright did not want the fact that Wittgenstein had appointed him a literary executor and not Malcolm to become a barrier between them. In any case, their friendship grew stronger in the subsequent years. Not long after von Wright’s proposal, Malcolm invited him to Cornell University. At that time, von Wright’s biographical sketch (1955) of Wittgenstein appeared for the first in English in The Philosophical Review, then edited by Malcolm. Staying at Cornell, von Wright taught a course on the Tractatus. Six students attended, so also did five staff members, among them, Malcolm himself, Max Black and John Rawls. 6 In contrast to earlier rather discouraging experiences in trying to explain Wittgenstein’s thought, 7 the course on the Tractatus at Cornell was an exhilarating experience, as he wrote to Elizabeth Anscombe:
I give seminars in which I try to explain the Tractatus. I have learned a lot from them and I have the feeling that now I am beginning to understand the book. It is even more wonderful than I had thought. And one of the most wonderful things about it is that it is absolutely straightforward. No metaphors, no allusions, no mystery. The difficulty is to avoid twisting his words, to avoid putting an “interpretation” on them. 8
With his enthusiasm for the poetic clarity of the Tractatus, von Wright got the inchoate idea to compile a collection of general remarks drawn from Wittgenstein’s manuscripts. He had brought to Cornell photographs of some manuscripts and was intent on typing out the passages that Rhees, Anscombe and he had chosen for the volume that would appear as Remarks on the Foundations of Mathematics (Wittgenstein 1956). It was the first time von Wright was centrally involved in editing a volume from Wittgenstein’s Nachlass. 9 Transcribing the selection was an unedifying experience at times, as he noted to Anscombe: “the work was awful. I am constantly tormented by the question: Do we do the right thing, or not?” 10 Still, while continuing to transcribe the selected passages, he was struck by the beauty of some remarks in the manuscripts:
Among the omitted stuff, there are many good remarks of a general nature. I have omitted them in order to avoid – as I think we should – creating the impression that the book, which we publish, is a collection of aphorisms. Perhaps some of the omitted remarks can be published on some other occasion. 11
This first observation of “some good remarks of a general nature” may be seen as the germ of CV. At that time, however, it did not occur to von Wright that these remarks might be related to Wittgenstein’s writings on the foundations of mathematics. Indeed, it took ten more years for the germ of CV to sprout, and yet almost another decade for von Wright to fully recognize the flower’s philosophical significance.
In the first half of the 1960s, Rhees systematically investigated the writings from Wittgenstein’s first years after his return to Cambridge in 1929 (cf. Erbacher et al. 2017). Both Rhees and von Wright were fascinated to discover that the writings in those manuscripts provide a bridge between the Tractatus and Philosophical Investigations. The first volume from those writings was Rhees’ edition Philosophische Bemerkungen (Wittgenstein 1964), which was intended as the first of two “intermediate cases” (Philosophical Investigations, § 122) in the morphology of Wittgenstein’s thinking. 12 The typescript of Philosophische Bemerkungen (Ts 209) stems from 1929/1930, the same time as Wittgenstein’s Lecture on Ethics (Ts 207, edited in Wittgenstein 1965). This caused Rhees to wonder if he ought to add the Lecture on Ethics to Philosophische Bemerkungen, or, alternatively, to combine it with a collection of remarks of a general nature. Von Wright addressed this consideration in a letter to Anscombe:
You may remember that Rhees in a letter raised the question of what to do with the lecture on Ethics. Chronologically it belongs in the period of the Philosophische Bemerkungen. Published as an Appendix to the Bemerkungen – with extract from Waismann’s notes – it would appear rather “out of place”. Rhees seems to feel the same, since he mentioned the possibility of publishing a separate volume consisting of general remarks on aesthetics, ethics, religion, etc. and including the Ethics lecture in it. This idea of a volume of “general remarks” is worth taking seriously. There are, for example, a number of remarks in the typescript of October 1948 to March 1949 which might go into such a volume and also in the typescript of last writings (i.a. the whole Notebook IV). We must discuss the problem when we meet. 13
The literary executors indeed discussed the issue during their next meeting in the summer of 1964, and they appointed von Wright to go through all the manuscripts in the Nachlass in order to make a selection for a volume of general remarks. Yet when he actually started making this selection, he soon became sceptical about the project and about ever publishing it, as he wrote to Anscombe in March 1965:
I have started to make a selection of “aphorisms” and “general remarks”. My impression so far is that the job is next to hopeless and will result in nothing publishable. But it can nevertheless be nice to have the selection made for one’s own (and your and Rhees’s) sake. 14
Only six days later, von Wright saw his first doubts confirmed:
I have been working on the selection now, but I am very pessimistic about the eventual publishability of anything. 15
He nevertheless continued searching the manuscripts, as he wrote to Anscombe:
As I think I told you in an earlier letter, I have been selecting “general remarks”, but become rather pessimistic about their publishability in one volume. In any case I am going to complete the job and compose a volume for you and Rhees, and me. It may be nice to have it in typescript, even it is unsuitable for publication. 16
After three and a half months, von Wright completed his task. The resulting first selection of general remarks amounts to two big folders containing more than 1,500 passages from about 60 items in Wittgenstein’s Nachlass. The typed selection is entitled thus:
A collection of remarks by Ludwig Wittgenstein
on questions connected with
his Life and Work; the Nature of Philosophical Inquiry;
Art, Religion and the “Philosophy of Life”; the I, the
Will, and the World; and various other General Topics 17
Von Wright sent a copy of this collection to each literary executor. In an accompanying letter, he explained the rationale for his selection:
I have proceeded on a “maximum principle”: selecting generously and with a view to then sieving the selected material. I doubt whether my present view of the matter is definitive: but it is against, rather than for, publishing anything at all. […] Perhaps some of us will some day have a really good idea of how to make a selection that can justifyable [sic] be published. 18
A note attached to the collection shows that the missing “justification” for a publication had to do with the assumed hiatus between Wittgenstein’s philosophical work and his general remarks:
One can make a broad distinction between remarks which are of Wittgenstein’s philosophical work and remarks which are “detached” or “detachable” from it. […] To the “detachable” remarks belong a great number of reflexions on art and religion. – Question: Could a collection be published consisting of only “detachable” remarks? Or would such a collection be too far removed from the rest of Wittgenstein’s work to be of interest? 19
While von Wright, in 1954, did not question whether it was right to separate the remarks of a general nature from those on the foundations of mathematics, he now wondered whether if there could be a justification to publish them by themselves. For the time being, the literary executors did not see such=a justification and thus did not publish them. This decision was in line with other cases where the literary executors excluded passages from publication-typescripts which they regarded as not belonging to Wittgenstein’s philosophical work. One of these cases is the editorial project that von Wright turned to after he had made the first selection of general remarks, namely, the project that developed from his and Malcolm’s idea to deposit copies of Wittgenstein’s writings at Cornell University. The way in which Wittgenstein’s private non-philosophical remarks were then discussed and handled sheds light on the hesitations to publish the general non-philosophical remarks in CV, especially as some of the former were eventually treated as part of the latter. 20