This discussion of the word 'world', and our frequent use of it have made it apparent that it is used in several ways. By unravelling these we can get an indication of the different kinds of phenomena that are signified, and of the way in which they are interconnected.
1. "World" is used as an ontical concept, and signifies the totality of those entities which can be present-at-hand within the world.
2. "World" functions as an ontological term, and signifies the Being of those entities which we have just mentioned. And indeed 'world' can become a term for any realm which encompasses a multiplicity of entities: for instance, when one talks of the 'world' of a mathematician, 'world' [65] signifies the realm of possible objects of mathematics.
3. "World" can be understood in another ontical sense—not, however, as those entities which Dasein essentially is not and which can be encountered within-the-world, but rather as that 'wherein' a factical Dasein as such can be said to 'live'. "World" has here a pre-ontological existentiell signification. Here again there are different possibilities: ''world" may stand for the 'public' we-world, or one's 'own' closest (domestic) environment.1
4. Finally, "world" designates the ontologico-existential concept of worldhood. Worldhood itself may have as its modes whatever structural wholes any special 'worlds' may have at the time; but it embraces in itself the a priori character of worldhood in general. We shall reserve the expression "world" as a term for our third signification. If we should sometimes use it in the first of these senses, we shall mark this with single quotation marks.
The derivative form 'worldly' will then apply terminologically to a kind of Being which belongs to Dasein, never to a kind which belongs to entities present-at-hand 'in' the world. We shall designate these latter entities as "belonging to the world" or "within-the-world" [weltzugehorig oder innerweltlich].
A glance at previous ontology shows that if one fails to see Being-in-the-world as a state of Dasein, the phenomenon of worldhood likewise gets passed over. One tries instead to Interpret the world in terms of the Being of those entities which are present-at-hand within-the-world but which are by no means proximally discovered-namely, in terms of Nature. If one understands Nature ontologico-categorially, one finds that Nature is a limiting case of the Being of possible entities within-the-world.
1 '... die "eigene" und nachste (hausliche) Umwelt.' The word 'Umwelt', which is customarily translated as 'environment', means literally the 'world around' or the 'world about'. The prefix 'urn-', however, not only may mean 'around' or 'about', but, as we shall see, can also be used in an expression such as 'urn zu ...', which is most easily translated as 'in order to'. Section 15 will be largely devoted to a study of several words in which this same prefix occurs, though this is by no means apparent in the words we have chosen to represent them: 'Umgang' ('dealings'); 'das Um-zu' ('the "in-order-to"'); 'Umsicht' ('circumspection').