Medieval concern for the various problems associated with the possibility of void space within the world was, as we have now seen, both extensive and intensive. This is hardly surprising when it is realized that every commentator on Aristotle's Physics had to confront a variety of arguments against the possible existence of empty space. With regard to the possibility that a vacuum might exist beyond the boundaries of the cosmos, the situation was quite different. For although, as will be seen, Aristotle had occasion in De caelo to reject extracosmic space, he considered the matter only briefly, and scholastic commentators on De caelo rarely used Aristotle's discussion as a point of departure for further speculation. In fact, brief discussions on extracosmic void were just as likely to turn up in commentaries on the Physics. Although Aristotle's arguments for the rejection of extracosmic void were to play a central role, the probable reason why the subject of extracosmic void did not become a regularly discussed theme in the Aristotelian commentary literature is the theological nature of the problem as it emerged in the Middle Ages during the thirteenth century. Although the historical roots of the concept of extracosmic void were both secular and theological, speculation about it became significant in the late Middle Ages only after it became enmeshed in theological debates about God's location, His absolute power, and the conditions that obtained before the creation.