Not surprisingly, Wittgenstein’s 1914-1916 Notebooks begin with concerns about logic and the problems he had discussed with Russell. As they progress, and as World War I drags on, however, we see the emergence of a series of themes seemingly distinct from the initial logical concerns. In particular, we see a concern with the self, the will, and ethics. From Wittgenstein’s letters we see that his experiences with the war have led him to Tolstoy and the gospels; we also see a renewed interest in Schopenhauer, among other figures. As Hans-Johann Glock (1999) notes, “in the Tractatus the allusions are less frequent and direct, but topics such as God, ethics, aesthetics, solipsism, the will, and mysticism are discussed in a Schopenhauerian spirit” (424).
To draw out these themes, the Tractatus must be supplemented with the Notebooks. In particular, it is important to look at the time-frame for Wittgenstein’s thoughts on solipsism, the issues and ideas that are wrapped up with his notes related to solipsism, and how these notes fit together with his rather austere remarks (even by Tractatus standards) in the 5.6s. For instance, an initial look at the Notebooks shows that these Schopenhauerian themes only emerge in the second half. Seeing this clearly then casts doubt on Max Black’s (1964) assertion, for example, that “parts of the [Tractatus] date back to 1913 and some of the concluding remarks on ethics and the will may have been composed still earlier, when Wittgenstein admired Schopenhauer” (1). The picture that emerges is in fact quite the reverse of this: Wittgenstein returns to Schopenhauer around 1915, and struggles afresh with Schopenhauerian themes through the end of the Notebooks.
The published notebooks open on August 22, 1914, but the first remark clearly pertaining to what Wittgenstein would say in the 5.6s doesn’t occur until May 23, 1915. Extending our scope, nothing directly relating to solipsism occurs in his 1913 notes on logic, or in his April 1914 notes to Moore. It is useful to get a picture of the relation of Wittgenstein’s train of thought (as captured in his notebooks) to the primary sections of the Tractatus that they relate to. Considering just the first two digits of Wittgenstein’s numbering, and color coding the second digit as shades of the first, we get a rough timeline (time reads left to right, then down – like a book; remarks with multiple bracketed references are shown above the primary references):
Focusing on the 5.6s, we see a decided trend of increasing concern. Zooming in on these passages, we see a characteristic pattern of thought dealing with the “will” that relates to issues of ethics, life and death, the mystical and God. Expanding our focus to include sections in the Tractatus clearly dealing with these issues (6.373, 6.374, 6.41, 6.42, 6.421, 6.423, 6.43, 6.431, 6.4311, 6.521, 6.432, 6.44, 6.522), the trend it yet more pronounced:
