The essay explores the possibilities afforded by Heidegger’s thought for addressing the question of the reality of the phenomenon within the framework of the theory of quantum mechanics. Heidegger’s conception of the task of phenomenology is seen to provide a crucial axis along which the phenomenon of quantum physics can be connected both to its appearance in language and to the historical unfolding of the horizon that grounds the possibility of an encounter with the phenomenon itself. The determinations of this (...) horizon, i.e. of the order of “phenomenality” that makes the appearance of the phenomenon possible, are analyzed in the instance of quantum mechanics, and compared to the ones presented by Heidegger in his considerations concerning the appearing of the phenomenon in Aristotelian and classical physics. The three main directives that structure the analysis of this order of phenomenality are the determinations of the conditions of experience of the phenomenon, of the function of language that makes this appearance possible, and of the subject function that constitutes, and is in turn constituted by, this experience. (shrink)