Why a hermeneutical philosophy of the natural sciences? It is necessary to address the philosophic crisis of realism vs relativism in the natural sciences. This crisis is seen as a part of the cultural crisis that Husserl and Heidegger identified and attributed to the hegemonic role of theoretical and calculative thought in Western societies. The role of theory is addressed using the hermeneutical circle to probe the origin of theoretic meaning in scientific cultural praxes. This is studied in Galileo's discovery (...) of the phases of Venus; the practice of measurement; the different theories and practices of space perception; the historicality and temporality of scientific research communities which ground paradigm change; and the process of discovery. The paper draws particularly from the work of Heidegger. Though envisaging all science and scholarship, the highlighted theme is research in the natural sciences. (shrink)