  Long before the Middle Ages, a well-defined tradition of writing commentaries on philosophical works had been established. It is perhaps natural, then, that the most common way of engaging philosophy throughout the Middle Ages consisted in writing commentaries on what were considered authoritative philosophical texts, and particularly works by Aristotle. So popular was commentary writing that thousands of Medieval Latin commentaries on Aristotle's writings are still extant, of which nearly two hundred concern the Categories (Lohr 1967, 1968, 1970, 1971, 1972, 1973). These commentaries were not always intended simply to explain texts; often, they became the means of developing the thoughts of the commentators on various philosophical topics. Moreover, commentators did not comment on Aristotle's works in isolation, but also consulted other commentaries on the same texts. In this way, they engaged and often challenged other interpretations, and developed their own insights.