  There is something useful, as a preliminary move, about interpreting the fourfold as a combination of nature and culture, but it is an idea that must be handled with care. For one thing, if what is meant by nature is the material world and its phenomena as understood by natural science, then Heidegger's account of the fourfold tells against any straightforward identification of earth and sky with nature. Why this is becomes clear once one sees how Heidegger describes the earth and the sky in Building Dwelling Thinking. “Earth is the serving bearer, blossoming and fruiting, spreading out in rock and water, rising up into plant and animal… The sky is the vaulting path of the sun, the course of the changing moon, the wandering glitter of the stars, the year's seasons and their changes, the light and dusk of day, the gloom and glow of night, the clemency and inclemency of the weather, the drifting clouds and blue depth of the ether” (351). What Heidegger's language here indicates is that the earth-as-dwelt-on and the sky-as-dwelt-under are spaces for a mode of habitation by human beings that one might call poetic rather than scientific. So, the nature of dwelling is the nature of the poet. In dwelling we inhabit the poetic (for discussion, see e.g., Young 2002, 99–100).