Ernst Mach’s definition of the relationship between thoughts and facts is well known, but the question of how Mach conceived of their actual relationship has received much less attention. This paper aims to address this gap in light of Mary B. Hesse’s view of a postempiricist approach to natural science. As this paper will show, this view is characterized by a constructivist conception of the relationship between theory and facts that seems to be consistent with Mach’s observations on scientific knowledge. (...) The paper first explores Hesse’s account of postempiricism and her project of a new epistemology. It then considers Ernst Mach’s conception of facts as the middle term of a triad of concepts that includes thoughts and elements as extreme terms. Finally, the paper will offer concluding remarks on Mach’s contribution to the debate on scientific realism and his attempt to redefine the notions of correspondence and objectivity in science. (shrink)