The glossary entry for truth from Barbara Bolt's Heidegger Reframed: Interpreting Key Thinkers for the Arts
truth (Wahr-heit) — To watch over and keep safe. Scientific approaches to truth are concerned with correctness, with defining criteria and establishing truth and falseness. According to the paradigm of propositional truth, there is a subject-knower and an object known. This sets up the structure for scientific knowing and scientific research. For Heidegger, this approach to truth ignores what truth means and what happens when truth is revealed. Disclosure is the essence of truth and truth is in the constant process of being revealed. Heidegger suggests that without Dasein there can be no truth. Dasein provides the clearing in which truth can happen. Everyday Dasein is Dasein fallen. Where that happens there is a closure that prevents the revelation of truth. This closes off or conceals truth. Thus in the structure of Dasein we see both openness and closure, truth and untruth. Here untruth is not a proposition that can be assessed in terms of falseness, but rather it is a reservoir of possibility of unconcealment.