 Put this broadly, Lewis’s position is indebted to Donald Davidson’s work, and Lewis frequently acknowledges the debt. But Lewis differs from Davidson in several respects. I’ll briefly mention four of them here, then look at two substantial changes in the next two sections. (The primary sources for the discussion in this section are “Radical Interpretation” (1974c) and especially its appendices in Philosophical Papers: Volume I (1983a), and “Reduction of Mind”.)