 The key step is the pragmatically licensed disjunction of contraries: if you assume I’ve made up my mind about the truth value of a given proposition \(p\) (e.g., “it will rain”) rather than being ignorant or undecided about it, then you will infer that I believe either \(p\) or \(\neg p\), and my denial that I believe the former (“I don’t think it will rain”) will lead you to conclude that I believe the latter (“I think it won’t rain”). (See Horn 1989, Chapter 5 for more on this phenomenon; Gajewski 2007 for a neo-Bartschian analysis; and Collins and Postal 2014 for a vigorous defense of a grammatical approach to neg-raising).