CRF Blog

What is logic?

by Bill Hayes

In What is logic? for Aeon, professor of philosophy Catarina Dutilh Novaes looks at the uses of logic.

The history of logic should be of interest to anyone with aspirations to thinking that is correct, or at least reasonable. This story illustrates different approaches to intellectual enquiry and human cognition more generally. Reflecting on the history of logic forces us to reflect on what it means to be a reasonable cognitive agent, to think properly. Is it to engage in discussions with others? Is it to think for ourselves? Is it to perform calculations?

In the Critique of Pure Reason (1781), Immanuel Kant stated that no progress in logic had been made since Aristotle. He therefore concludes that the logic of his time had reached the point of completion. There was no more work to be done. Two hundred years later, after the astonishing developments in the 19th and 20th centuries, with the mathematisation of logic at the hands of thinkers such as George Boole, Gottlob Frege, Bertrand Russell, Alfred Tarski and Kurt Gödel, it’s clear that Kant was dead wrong. But he was also wrong in thinking that there had been no progress since Aristotle up to his time. According to A History of Formal Logic (1961) by the distinguished J M Bocheński, the golden periods for logic were the ancient Greek period, the medieval scholastic period, and the mathematical period of the 19th and 20th centuries. (Throughout this piece, the focus is on the logical traditions that emerged against the background of ancient Greek logic. So Indian and Chinese logic are not included, but medieval Arabic logic is.)

Why did Kant disregard the scholastic tradition? And, more generally, what explains the ‘decline’ of logic after the scholastic period? Though in the modern era logic remained an important part of the educational curriculum, there were no fundamental innovations to speak of (with the important exception of some developments in the 17th century, by Gottfried Wilhelm Leibniz). In fact, much of the scholastic achievement got lost, and the logic taught in this period (the one Kant was referring to) was for the most part rudimentary. [more]