Joseph Rouse has drawn from Heidegger's early philosophy to develop what he calls a "practical hermeneutics of science." With this, he has not only become an important player in the recent trend towards practice-based conceptualisations of science, he has also emerged as the predominant expositor of Heidegger's philosophy of science. Yet, there are serious shortcomings in both Rouse's theory of science and his interpretation of Heidegger. In the first instance, Rouse's practical hermeneutics appears confused on the topic of realism. In the second instance, Rouse suppresses Heidegger's distinction between existence and essence, and hence fails to grasp the latter's corollary distinction between scientific research and everyday practice. I argue that, by accepting a correction in his interpretation of Heidegger, Rouse would find the means to resolve the debilitating tensions in his stance towards realism.