  Whether or not unconcealing ought to count as a species of truth, it is arguable that the place which it (along with its partner structure, Reality) occupies in the Heideggerian framework must ultimately threaten even the mild kind of scientific realism that we have been attributing, somewhat tentatively, to Heidegger. The tension comes into view just at the point where unconcealing is reinterpreted in terms of Dasein's essential historicality. Because intelligibility, and thus unconcealing, has an essentially historical character, it is difficult to resist the thought that the propositional and instrumental truths generated out of some specific field of intelligibility will be relativistically tied to a particular culture in a particular time period. Moreover, at one point, Heidegger suggests that even truth as revealed by science is itself subject to this kind of relativistic constraint. Thus he says that “every factical science is always manifestly in the grip of historizing” (Being and Time 76: 444). The implication is that, for Heidegger, one cannot straightforwardly subject the truth of one age to the standards of another, which means, for example, that contemporary chemistry and alchemical chemistry might both be true (cf. Dreyfus 1990, 261–2). But even if this more radical position is ultimately Heidegger's, there remains space here for some form of realism. Given the transcendental relation that, according to Heidegger, obtains between fields of intelligibility and science, the view on offer might still support a historically conditioned form of Kantian empirical realism with respect to science. Nevertheless it must, it seems, reject the full-on scientific realist commitment to the idea that the history of science is regulated by progress towards some final and unassailable set of scientifically established truths about nature, by a journey towards, as it were, God's science (Haugeland 2007).