In Descartes we find the most extreme tendency towards such an ontology of the 'world', with, indeed, a counter-orientation towards the res cogitans—which does not coincide with Dasein either ontically or ontologically. The analysis of worldhood which we are here attempting can be made clearer if we show how it differs from such an ontological tendency. Our analysis will be completed in three stages: (A) the analysis of environmentality and worldhood in general; (B) an illustrative contrast between our analysis of worldhood and Descartes' ontology of the 'world'; (C) the aroundness [das Umhafte] of the environment, and the 'spatiality' of Dasein.1
A. Analysis of Environmentality and Worldhood in General
¶ 15. The Being of the Entities Encountered in the Environment
The Being of those entities which we encounter as closest to us can be exhibited phenomenologically if we take as our clue our everyday Beingin- the-world, which we also call our "dealings"2 in the world and with entities within-the-world. Such dealings have already dispersed themselves  into manifold ways of concern.3 The kind of dealing which is closest to us is as we have shown, not a bare perceptual cognition, but rather that kind of concern which manipulates things and puts them to use; and this has its own kind of 'knowledge'. The phenomenological question applies in the first instance to the Being of those entities which we encounter in such concern. To assure the kind of seeing which is here required, we must first make a remark about method.
In the disclosure and explication of Being, entities are in every case our preliminary and our accompanying theme [ das Vor-und Mitthematische]; but our real theme is Being. In the domain of the present analysis, the entities we shall take as our preliminary theme are those which show themselves in our concern with the environment. Such entities are not thereby objects for knowing the 'world' theoretically; they are simply what gets used, what gets produced, and so forth. As entities so encountered, they become the preliminary theme for the purview of a 'knowing' which, as phenomenological, looks primarily towards Being, and which, in thus taking Being as its theme, takes these entities as its accompanying theme. This phenomenological interpretation is accordingly not a way of knowing those characteristics of entities which themselves are [seiender Beschaffenheiten des Seienden]; it is rather a determination of the structure of the Being which entities possess.
1 A is considered in Sections 1 5-18; B in Sections 19-21; C in Sections 22-24.
2 'Umgang'. This word means literally a 'going around' or 'going about', in a sense not too far removed from what we have in mind when we say that someone is 'going about his business'. 'Dealings' is by no means an accurate translation, but is perhaps as convenient as any. 'Intercourse' and 'trafficking' are also possible translations.
3 See above, H. 57, n. 1, p. 83.