This term does not express any negative evaluation, but is used to signify that Dasein is proximally and for the most part alongside the 'world' of its concern. This "absorption in ..." [Aufgehen bei ...] has mostly the character of Being-lost in the publicness of the "they". Dasein has, in the first instance, fallen away [abgefallen] from itself as an authentic potentiality for Being its Self, and has fallen into the 'world'.1 "Fallenness" into the 'world' means an absorption in Being-with-one-another, in so far as the latter is guided by idle talk, curiosity, and ambiguity. Through the Interpretation of falling, what we have called the "inauthenticity" of [176] Dasein may now be defined more precisely. On no account, however, do the terms "inauthentic" and "non-authentic" signify 'really not',2 as if in this mode of Being, Dasein were altogether to lose its Being. "Inauthenticity" does not mean anything like Being-no-longer-in-the-world, but amounts rather to a quite distinctive kind of Being-in-the-world—the kind which is completely fascinated by the 'world' and by the Dasein-with of Others in the "they". Not-Being-its-self [Das Nicht-es-selbst-sein] functions as a positive possibility of that entity which, in its essential concern, is absorbed in a world. This kind of not-Being has to be conceived as that kind of Being which is closest to Dasein and in which Dasein maintains itself for the most part.
So neither must we take the fallenness of Dasein as a 'fall' from a purer and higher 'primal status'. Not only do we lack any experience of this ontically, but ontologically we lack any possibilities or clues for Interpreting it.
In falling, Dasein itself as factical Being-in-the-world, is something from which it has already fallen away. And it has not fallen into some entity which it comes upon for the first time in the course of its Being, or even one which it has not come upon at all; it has fallen into the world, which itself belongs to its Being. Falling is a definite existential characteristic of Dasein itself. It makes no assertion about Dasein as something present-at-hand, or about present-at-hand relations to entities from which Dasein 'is descended' or with which Dasein has subsequently wound up in some sort of commercium.
We would also misunderstand the ontologico-existential structure of falling3 if we were to ascribe to it the sense of a bad and deplorable ontical property of which, perhaps, more advanced stages of human culture might be able to rid themselves.
1 '... und an die "Welt" verfallen.' While we shall follow English idioms by translating 'an die "Welt"' as 'into the "world"' in contexts such as this, the preposition 'into' is hardly the correct one. The idea is rather that of falling at the world or collapsing against it.
2 'Un- und nichteigentlich, bedeutet aber keineswegs "eigentlich nicht" ...'
3 'Die ontologisch-existenziale Struktur des Verfallens ...' The words 'des Verfallens' do not appear in the earlier editions.