Earlier version of this paper were read at the conference "Looking Back, Looking Forward: Philosophy, Its History and Future: A Conference to Celebrate the Centenary of the Doctoral Program at the University of Toronto," October 25, 1997; to the Medieval Studies Institute (Indiana University), September 27, 1999; and to the Purdue Philosophy Colloquium, November 2, 2000.A talk highlighting four examples of a peculiar problem facing historians of late medieval logic and semantic theory. While we often know a great deal about the mechanics and details of many of the theories during this period, we too often don't know exactly what the theories were about! The talk discusses four examples of this: (a) the theory of "obligationes," (b) "exposition" or "exponibles," (c) "proofs of propositions," and (d) the theory of "supposition.
