 It is important to note that Feigl’s version of the identity theory is not without precursors. It has even been argued that “[s]een against the backdrop of nineteenth-century German and Austrian philosophy, Feigl’s approach was neither novel nor audacious; he merely revived a tradition that had once been a mainstream topic turned unfashionable; to be exact, he modified and spelled out one specific traditional position” (Heidelberger 2003, p. 234). This might be exaggerated, but it can hardly be contested that Feigl, in his treatment of the mind-body problem, was (again) committed to the critical realist accounts of Alois Riehl (cf. Riehl 1879, 1881, 1887; further Röd 2001) and especially of the early (pre-Viennese) Schlick (see the entry on  Moritz Schlick).  As Feigl himself frequently pointed out, it was the early Schlick’s “double-knowledge” or “double-language” theory that exerted the greatest influence upon his own approach (see, for example, Feigl 1981, p. 288). In a nutshell, Schlick, in his General Theory of Knowledge (1918; 1925), had argued that the difference of the mental and the physical is a difference between two conceptual systems and not a difference between two areas of reality. It was, in other words, an epistemological rather than a metaphysical problem (cf. Schlick 1974, p. 300). According to Schlick, the “relation between immediately experienced reality and the physical brain processes is […] no longer one of causal dependency but of simple identity. What we have is one and the same reality, not ‘viewed from two different sides’ or ‘manifesting itself in two different forms’, but designated by two different conceptual systems, the psychological and the physical” (ibid., p. 299). It was this very line of thought that confirmed Feigl in his conviction that “the mind-body problem is not a pseudoproblem” (Feigl 1981, p. 349).