become his own authentic self. Here I certainly do not understand the other existence primarily in terms of the world I’m concerned about. Rather, I understand the other’s existence only in terms of himself. By contrast, the first mode of being concerned-for is concerned for the other in such a way that, in his place and at his service, it procures for him a possible possession. It understands the other existence in terms of the things that he is concerned about, which are giving him difficulty. This concern-for throws the other out of his place, as it were, and engages only with what must be done  to restore the other to a now- guaranteed possession of that thing. This kind of being concerned-for treats the other like a nothing, as if he had nothing of existence about him. In this form of being concerned-for he is not present as his own existence but as inauthentic existence, as something merely there in the world, someone who cannot get anywhere with his life.
We have characterized two extreme modes of being concerned-for—the one authentic, the other inauthentic—because only from out of these two extremes can we shed some light on those factical concretions that we understand as “mixed forms” (for reasons that are embedded in existence itself and cannot be further explained here).
Existence’s being-with-and-for-each-other, as existential, is an a priori being-with-and-for-each-other in the world and thus also a mode of being concerned about the world that is exercised with-and-for-each-other. The two kinds of such being-concerned-about the world are ontologically different, depending on the kind of being-concerned-for that the concern has and on the character of care itself. Likewise the lived world, or particular things within it, can be objects of concern in different ways, depending on how each existence relates to the lived world and is engaged with it and for a specific being concerned-about. In that case, being-with-each-other is determined simply by how people deal with the same thing.
The possibilities of for-each-other are confined within certain limits. For example, in being-for-each-other there can be distance and reserve, not to mention outright mistrust. However, in the opposite direction, being-with-each-other can also be determined not from the thing with and for which they are engaged but from each one’s own existence that is with the other. From that bondedness with the other there can first arise the authentic issue, i.e., the correct concern about the same issue. Only from that does “communication” (as we now call it) arise. So we see a peculiar conjunction between the two phenomena: on the one hand, the being-with-each-other of being concerned-for, and on the other, being concerned about the world itself. 
If we hope to understand the phenomenon of being concerned-about as the kind of being with which existence is in the world—we must understand this concept in a sufficiently broad sense. That is, we