William Heytesbury (c. 1313–1372) was a prominent medieval English philosopher, logician, and mathematician known for his contributions to the fields of logic, natural philosophy, and metaphysics. He was one of the leading figures of the Oxford Calculators, a group of scholars at the University of Oxford who made significant advances in the field of mathematics and logic during the 14th century.
Early Life and Education
William Heytesbury was born in the early 1310s in the town of Heytesbury, Wiltshire, England. He studied at the University of Oxford and earned his Bachelor of Arts degree in 1332 and his Master of Arts degree in 1337. He went on to become a fellow of Merton College, Oxford, where he spent most of his academic career.
Contributions to Logic and Mathematics
Heytesbury was a key figure in the development of medieval logic and mathematics. He made important contributions to the fields of propositional logic, syllogistic logic, and the theory of obligationes, a type of logical debate that was popular during the medieval period.
Heytesbury’s work in propositional logic involved the study of statements that are either true or false. He developed a system of propositional logic that involved the use of truth tables, which are tables that show all possible combinations of truth values for a given set of propositions. Heytesbury’s work in propositional logic was a significant step forward in the development of modern symbolic logic.
Heytesbury also made significant contributions to the field of syllogistic logic, which deals with the relationships between propositions that involve terms such as “all,” “some,” and “none.” He developed a system of syllogistic logic that involved the use of diagrams, which helped to make the logical relationships between propositions more visually apparent.
In addition to his work in logic, Heytesbury was also a notable mathematician. He made important contributions to the study of infinity, including the concept of infinite sets and the distinction between actual and potential infinity. He also made significant advances in the field of trigonometry, developing methods for calculating the sine and tangent of angles.
Contributions to Natural Philosophy and Metaphysics
Heytesbury was also a prominent figure in the fields of natural philosophy and metaphysics. He developed a theory of motion that involved the study of impetus, a concept that describes the force that causes a moving object to continue moving. Heytesbury’s theory of impetus was a significant precursor to the modern concept of inertia.
Heytesbury also made contributions to the field of metaphysics, particularly in his discussions of causation and the nature of universals. He argued that there is no necessary connection between cause and effect, and that causation is only a matter of habit or custom. He also developed a theory of universals that rejected the notion that there is a single universal form that is shared by all instances of a particular kind of thing.
Legacy
William Heytesbury’s contributions to logic, mathematics, natural philosophy, and metaphysics were significant and influential. His work in propositional logic and syllogistic logic helped to lay the groundwork for the development of modern symbolic logic. His contributions to the study of infinity and trigonometry were also important in the development of modern mathematics.
Heytesbury’s theories of motion and impetus were influential in the development of modern physics, particularly in the work of Galileo and Newton. His rejection of the notion of necessary connection in causation was also influential in the development of later philosophical traditions, including empiricism and pragmatism.