Substantive changes in this period include,

• 12/20/20: Repair for T13.57j,m. Includes new theorems in chapter 13 (and consequent renumbering of others).
• 11/29/20: Small chapter 11 changes to clarify that sets of sentences and classes of models are language-relative.
• 11/18/20: Clean up T11.15.
• 11/15/20: Simplification and strengthening of T10.5 (and deletion of corresponding proof exercise).
• 11/13/20: Reorganization and revision to T13.12–13.14 (again, sigh).
• 11/9/20: Cleanup and fix to T11.31.
• 11/3/20: Fix chapter 7 statement for definition by (abv).
• 11/2/20: Revision of T13.13 case for (o). I keep fighting with this.
• 10/30/20: E8.16 is new (with renumbering of subsequent chapter 8 exercises).
• 10/28/20: Reorganization and cleanup of 13.6.2 reasoning that Godel’s second theorem implies Lob’s theorem.
• 10/21/20: Clean up formulas vs sentences, especially in chapter 11.
• 10/17/20: Formulation of T12.23 and T14.6 reflects restriction to languages extending \mathcal{L_{\mathrm{\scriptscriptstyle{NT}}}}.
• 10/16/20: Reasoning for T12.20 accounts for theorems that are not sentences.
• 10/16/20: log start date.

T.R.