 De Morgan’s book of 1847 was part of a revival in logic studies that originated at the beginning of 19th Century with Joseph Diez Gergonne (1771–1859) in France, and Bernhard Bolzano (1781–1848) in Bohemia, among others. George Bentham and William Hamilton in the United Kingdom were also part of this revival and their studies focused on the nature of variations of the categorical sentences in traditional syllogistic, including what was called “quantification of the predicate”; for example, “All \(A\) are some \(B\)” or “Some \(A\) are all \(B\)”. It was thought that this problem required an extension of the syllogistic logic of Aristotle and that some form of symbolic method was needed both to handle such statements and provide a classification of their different types (see Heinemann 2015 chapters 2 and 3). 