 It is easy to see that, combined with the rejection of rational intuition, the Vienna Circle’s exclusive apportionment of reason into either formal a priori reasoning, issuing in analytic truths (or contradictions), and substantive a posteriori reasoning, issuing in synthetic truths (or falsehoods), severely challenged the traditional understanding of philosophy. All members of the Circle hailed the end of distinctive philosophical system building. In line with the Tractatus claim that all philosophy is really a critique of language, the Vienna Circle took the so-called linguistic turn, the turn to representation as the proper subject matter of philosophy. Philosophy itself was denied a separate first-order domain of expertise and declared a second-order inquiry. Whether the once queen of the sciences was thereby reduced to the mere handmaiden of the latter was still left open. It remained a matter of disagreement what type of distinctively philosophical insight, if any, would remain legitimate. Just as importantly, however, the tools of modern logic were employed also for metatheoretical construction, not just for the reduction of empirical claims to their observational base or, more generally, for the derivation of their observational consequences. For the price of abandoning foundationalist certainty this allowed for an enormous expansion of the domain of empirical discourse. Ultimately, it opened the space for the still ongoing discussions of scientific realism and its alternatives (see section 3.4 below).