 Aristotle’s theory of the syllogism for assertoric (non-modal) sentences was a remarkable achievement and virtually complete in the Prior Analytics. To quote Kant, it was “a closed and completed body of doctrine.” Medieval logicians could not add much to it, though small changes were sometimes made and it was systematized in different ways. It was not until the mid-fourteenth century, when John Buridan reworked logic in general and placed the theory of the syllogism in the context of the more comprehensive logic of consequence, that people’s understanding of syllogistic logic began to change.