A Letter from Kripke to Lewis

The following is a typeset copy of a letter sent by Saul Kripke to David Lewis on August 11, 1969 regarding the article “Counterpart Theory and Quantified Modal Logic” (Lewis, 1968). The original letter was typeset by Mimi Foster (indicated by the initials “mf” at the end of the letter) at Rockefeller University. In consultation with Saul Kripke, we corrected some typos, filled in blank formulas, and added three footnotes. Keywords have been added before the letter, references have been added after the letter, and the original pagination of the letter is reflected in bracketed parentheticals. (The Editors.)