  So, human beings dwell in that they stay (are at home) on the earth, under the sky, before the divinities, and among the mortals (that is, with one another as mortals). It is important for Heidegger that these dimensions of dwelling are conceived not as independent structures but as (to use a piece of terminology from Being and Time) ecstases—phenomena that stand out from an underlying unity. That underlying unity of earth, sky, divinities and mortals—the ‘simple oneness of the four’ as Heidegger puts it in Building Dwelling Thinking (351)—is what he calls the fourfold. The fourfold is the transformed notion of world that applies within the later work (see e.g., The Thing; for an analysis of the fourfold that concentrates on its role as a thinking of things, see Mitchell 2010). It is possible to glimpse the character of the world-as-fourfold by noting that whereas the world as understood through Being and Time is a culturally conditioned structure distinct from nature, the world-as-fourfold appears to be an integrated combination of nature (earth and sky) and culture (divinities and mortals). (Two remarks: First, it may not be obvious why the divinities count as part of culture. This will be explained in a moment. Secondly, the later Heidegger sometimes continues to employ the sense of world that he established in Being and Time, which is why it is useful to signal the new usage as the transformed notion of world, or as the world-as-fourfold.)