conceding the 'certainty' of death in this ambiguous manner just in order  to weaken that certainty by covering up dying still more and to alleviate its own thrownness into death
By its very meaning, this evasive concealment in the face of death can not be authentically 'certain' of death, and yet it is certain of it. What are we to say about the 'certainty of death'?
To be certain of an entity means to hold it for true as something true.1 But "truth" signifies the uncoveredness of some entity, and all uncoveredness is grounded ontologically in the most primordial truth, the disclosedness of Dasein.XIV As an entity which is both disclosed and disclosing, and one which uncovers, Dasein is essentially 'in the truth'. But certainty is grounded in the truth, or belongs to it equiprimordially. The expression 'certainty', like the term 'truth', has a double signification. Primordially "truth" means the same as "Being-disclosive", as a way in which Dasein behaves. From this comes the derivative signification: "the uncoveredness of entities". Correspondingly, "certainty", in its primordial signification, is tantamount to "Being-certain", as a kind of Being which belongs to Dasein. However, in a derivative signification, any entity of which Dasein can be certain will also get called something 'certain'.
One mode of certainty is conviction. In conviction, Dasein lets the testimony of the thing itself which has been uncovered (the true thing itself) be the sole determinant for its Being towards that thing understandingly.2 Holding something for true is adequate as a way of maintaining oneself in the truth, if it is grounded in the uncovered entity itself, and if, as Being towards the entity so uncovered, it has become transparent to itself as regards its appropriateness to that entity. In any arbitrary fiction or in merely having some 'view' ["Ansicht"] about an entity, this sort of thing is lacking.
The adequacy of holding-for-true is measured according to the truth-claim to which it belongs. Such a claim gets its justification from the kind of Being of the entity to be disclosed, and from the direction of the disclosure. The kind of truth, and along with it, the certainty, varies with the way entities differ, and accords with the guiding tendency and extent of the disclosure. Our present considerations will be restricted to an
1 'Eines Seienden gewiss-sein besagt: es als wahres für wahr halten.' The earlier editions have 'Gewisssein' instead of 'gewiss-sein'. Our literal but rather unidiomatic translation of the phrase 'für wahr halten' seems desirable in view of Heidegger's extensive use of the verb 'halten' ('hold') in subsequent passages where this phrase occurs, though this is obscured by our translating 'halten sich in . . .' as 'maintain itself in . . .' and 'halten sich an . . .' as 'cling to . . .' or 'stick to . . .'.
2 'In ihr lässt sich das Dasein einzig durch das Zeugnis der entdeckten (wahre) Sache selbst sein verstehendes Sein zu dieser bestimmen.' The connection between 'Überzeugung' ('conviction') and 'Zeugnis' (testimony) is obscured in our translation.