Practically speaking, one must perhaps at some point confront the meaning of the word “must.” Salmon had done so. His study on the matter is:
“Conventional Implicature, Presupposition, and the Meaning of Must,” William Salmon [pictured here], Journal of Pragmatics, vol. 43, no. 14, November 2011, pp. 3416-3430. The author is at the University of British Columbia, Canada.
BONUS: Note that the Journal of Pragmatics finds it practical to use page numbering that goes into the thousands.