Here is the intro to Giandomenica Becchio’s paper:
In the Preface of The Sensory Order, Hayek stated that this book was based on his readings in psychology during 1919–1920, when he was still a young student in Vienna interested in both psychology and economics. Among many others, Hayek explicitly cited Mach’s influence on him. Hayek’s contacts with the lively Viennese milieu during the 1920s and 1930s had a fundamental role in the story of the use of Mach in Hayek’s book. As Hayek himself explained, Mach had a great influence on Viennese students and scholars until the 1930s, because he represented ‘‘the only source of arguments against a metaphysical and nebulous attitude’’ that was spreading among scientists (Blackmore, Itagaki, & Tanaka, 2001, p. 124). The use of Mach’s philosophy as a tool against any metaphysical attitude was particularly strong inside the Vienna Circle, where scholars like Otto Neurath and Rudolph Carnap had founded the Ernst Mach Society (Verein Ernst Mach, 1927) to support their movement and to link Mach’s empiricism to their philosophical approach,which they later named ‘‘logical positivism’’ (Blumberg & Feigl, 1931). Hayek strongly criticized the Vienna Circle’s philosophical approach: he mainly rejected Neurath’s physicalism (the belief that all science ultimately reduces to the laws of physics, Neurath, 1931; Caldwell, 2004), even if he showed some interest in Carnap’s logical system (Carnap, 1928). When Hayek introduced the system of multiple classification in The Sensory Order, he cited Carnap as the one who provided ‘‘a somewhat similar statement of the problems of the order of sensory qualities’’ (Hayek, 1952, p. 51). Nevertheless, in the mid-1930s, when Carnap officially subscribed to Neurath’s physicalism, it culminated in the project of the unification of science (Stadler, 2001).1 Hayek’s aversion arose: From the fact that we shall never be able to achieve more than an ‘explanation of the principle’ by which the order of mental events is determined, it also follows that we shall never achieve a complete ‘unification’ of all sciences in the sense that all phenomena of which it treats can be described in physical term. (Hayek, 1952, p. 191)
And in the following footnote he specifically named both Carnap and Neurath: their physical language, since it refers to the phenomenal or sensory qualities of the objects, is not ‘‘physical’’ at all. Their use of this term rather implies a metaphysical belief in the ‘‘ultimate reality’’ and constancy of the phenomenal world for which there is little justification. (ibid.) In this passage Hayek accused them of having dropped their original antimetaphysical attitude – mediated through Mach – to propose a new form a metaphysical belief, based on the reduction of any reality to the empirical realm. Hayek’s j’accuse is significant: for 30 years the philosophers of the Vienna Circle claimed Mach’s philosophy as one of the main sources of their aversion to metaphysics and a pillar of their philosophical approach based on a new form of positivism.2 In the International Encyclopedia of Unified Science, Joergensen explained the three common traits between ‘‘Mach’s positivism’’ and the Vienna Circle philosophy: the idea that ‘‘human knowledge is a biological phenomenon’’; the rejection of any form of ‘‘thing-in-itself’’ (and for that matter, of any form of Kantianism) and the overlap between physical reality and physical elements (Joergensen, 1951, p. 853). To explain the link between Mach and Hayek on the one hand and Hayek’s aversion to the logical positivism (apparently and ‘‘officially’’ rooted in Mach’s philosophy) on the other hand, we need to consider what Hayek meant when he mentioned Mach’s influence in The Sensory Order.