Whereas the previous chapter investigated the Kaʿba in terms of its exteriority, this and the next chapter investigate it in terms of its interiority. Having drawn ever nearer to the Kaʿba, from the world born of the Kaʿba and the settlements and sites oriented to the Kaʿba, then to the Kaʿba's foundations and walls, we finally look inside. In this and the subsequent chapter, the book's final chapter, we examine how and what the House houses and thereby fulfils a basic function of architecture: to shelter and hold.

Counter-intuitively, the cloth that robes the Kaʿba's exterior, the Kiswa, forms a significant element of this inward-looking inquiry; for, as will be shown in the final chapter, in many verbal and visual representations of the Kaʿba it tells whether the House is empty or full. That is to say, in the second part of this inquiry into the sheltering function of the Kaʿba, I shall argue that a particular way of hanging the Kiswa annually signals when a superabundant, divine presence is imagined to be residing within the Kaʿba. This signalling forms a lesser-known function of the Kaʿba's robe.

The present chapter will focus on the first part of this inquiry. I shall argue that the total emptiness of the Kaʿba in terms of cultic content and its near emptiness in terms of material content are part of the House’s function as a placeholder of the symbolic order of Islam. This function, I shall show, is similar to the function of zero in cultures historically stamped by visualising technologies based on linear perspective.

The chapter will proceed as follows: first, an account of what the early Islamic sources say the Kaʿba held before the advent of Islam, what they say this content was for, and what they allege the Prophet did with it upon his conquest of Mecca; second, a discussion of the sources’ claim that the Prophet evacuated most of this content, and an analysis of diagrams of the Kaʿba which substantiate this claim; and third, an interpretation of the resultant emptied House as the placeholder of a void that is (1) functional in Islamic culture, anchoring the symbolic order of Islam, and (2) constitutive of the House's mystery.