We develop some of Williamson’s ideas regarding how propositional calculus aids in comprehending Aristotelian logic. Specifically, we enhance the utilisation of truth tables to examine the structure of opposition diagrams. Using ‘conditioned truth tables’, we establish logical dependency relationships between the truth values of different propositions. This approach proves effective in interpreting various texts of the Organon concerning the doctrine of opposition.

This paper investigates whether Aristotle was aware of the fourth figure, and if he was aware of the fourth figure, why he excluded it from his system. Various commentators have explained why this figure does not exist in the system, so this paper compiles ane examines these arguments through a certain logical frame. By inquiring into why the fourth figure was not included in his logical system, the paper considers whether logical factors may explain this exclusion.