Detecting the Logical Content: Burley's 'Purity of Logic'

In one of his inaugural lectures Dov Gabbay demonstrated God’s providence as follows—I quote from memory. God had seen fit to send his revelation to mankind in a language with no verb tenses. (In classical Hebrew the verb forms are distinguished as perfective, imperfective, passive, reduplicative, etc., but not as past, present or future.) So there was a problem to explain how facts about a temporal world can be expressed in a language with no tenses. Logicians could not only solve this problem; they could also apply for research grants for solving it. Thus God ensured that logicians would not go short of spare cash. As a hardened atheist, what can I rescue from this story? Actually, quite a lot. In the history of logic we study texts that are written in a language generally quite different from our own, on subjects that supposedly have something to do with what we understand as logic. The links are often hard to make. One thing that historians of logic do is to describe the deductive practices of earlier thinkers. In this sense Netz’s [13] close study of Euclid’s procedures is an important contribution to the history of Greek logic. Here I try to make a small step in the same direction with a medieval logician. But reconstructing practices is not enough. Netz remarks [13, p. 216]: