Project title

Wallis’s Treatise of Logick

Image for LogicJohn Wallis’s Institutio Logicae was first published in Latin in 1687 but its origins lay in an unpublished Treatise of Logick, which had been composed possibly as early as the 1650s. As with his Grammar, it is thus possible to document the development of his thought over several decades.

Logic had a prominent place in the undergraduate curriculum in seventeenth-century Oxford, and this student body was clearly Wallis’s intended audience. His treatment of logic was not meant to be innovative, but it differs from traditional Aristotelian practice in certain key respects, notably his treatment of singular propositions, i.e. those in which terms referring to individuals occur. Aristotle had excluded propositions of this kind from his syllogistic; Wallis proposed an ingenious analysis whereby singular propositions can be treated as a subclass of universal ones.

The dominance of Aristotelian logic in the mid-seventeenth-century curriculum was a matter of intense controversy. The wider context of Wallis’s writings on logic, both institutional and intellectual, was explored in the first symposium of the project, organized jointly by the Wallis project and the Institute for Logic, Language and Computation at the University of Amsterdam. Papers were presented on topics including the status of logic as a discipline, the employment of logic in other fields such as philosophy and theology, and the question of how Wallis’s approach differs from that of other theoreticians and practitioners both in England and on the continent.

Tree of Porphyry - print (pdf)

Tree of Porphyry - manuscript (pdf)