co-attunement with others, but it is not necessarily being afraid with them or even being afraid together. One can be afraid for ... without being afraid oneself. But viewed precisely, fearing for ... is, after all, being afraid oneself. What is "feared" here is the being-with the other who could be snatched away from us. What is fearsome is not aimed directly at the one who is fearing with. Fearing for ... knows in a way that it is unaffected and yet is affected in the involvement of Dasein-with for whom it is afraid. It is not a matter here of degrees of "feeling tones," but of existential modes. Fearing for . .. does not lose its specific genuineness when it is "really" not afraid.
The factors constitutive for the full phenomenon of fear can vary. Thus various possibilities of fear result. Approaching nearby belongs to the structure of encountering what is threatening. When something threatening itself suddenly bursts into heedful being-in-the-world in its character of "not right now, but at any moment," fear becomes alarm. Accordingly, we must distinguish in what is threatening the nearest approach of what threatens and the way in which this approach itself is encountered, namely, its suddenness. What we are alarmed about is initially something known and familiar. But when what threatens has the character of something completely unfamiliar, fear becomes horror. And when something threatening is encountered in the aspect of the horrible, and at the same time is encountered as something alarming, suddenness, fear becomes terror. We are familiar with further variations of fear,· such as timidity, shyness, nervousness, misgiving. All modifications of fear as possibilities of attunement point to the fact that Dasein as being-in-the-world is "fearful." This "fearfulness" must not be understood in the ontic sense of a factical, "isolated" tendency, but rather as the existential possibility of the essential attunement of Dasein in general, which is, of course, not the only one.
§ 31. Da-sein as Understanding
Attunement is one of the existential structures in which the being [Sein] of the "there" dwells. Equiprimordially with it, understanding constitutes this being [Sein]. Attunement always has its understanding, [143] even if only by suppressing it. Understanding is always attuned. If we interpret understanding as a fundamental existential,* we see that this phenomenon is conceived as a fundamental mode of the being of Dasein. On the other hand, "understanding" in the sense of one possible kind of cognition among others, distinguished as "explaining," must be interpreted, like explaining, as an existential derivative of the primary understanding which constitutes the being of the there in general.
* Fundamental ontology, that is, from the relation of the truth of being.