Entries for Nietzsche's private library project - Ernst Mach

Gori / Mach_NB 1 Nietzsches Bibliothek – digitale Edition und philosophischer Kommentar [A] E. Mach, Beiträge zur Analyse der Empfindungen, Jena, G. Fischer 1886 Abstract: In Beiträge zur Analyse der Empfindungen (BN/mach-1886)*, the Austrian physicist Ernst Mach explores issues related to the physiology of sense organs and defends a monistic standpoint according to which the contraposition between physical and psychical is merely theoretical. Aim of this book is to get science rid of metaphysical obscurities and provide new boundaries for the inquiry. Mach especially rejects the I as substance-concept in a way that reminds Nietzsche’s late anti-cartesianism. More in general, similarities between Nietzsche’s and Mach’s views can be found, even if it is not possible to demonstrate a direct influence of the latter on the former. Keywords: Subjectivity, Physiology, Monism, Anti-metaphysics, Empiricism 1. Ernst Mach’s neutral monism Ernst Mach (1838-1916) was a major figure in the field of physics, at Nietzsche’s time. His study on the science of mechanics (Die Mechanik in ihrer Entwicklung, historischkritisch dargestellt, 1883) and his essays on various epistemological issues (Die Prinzipien der Wärmelehre, 1896; Populär-wissenschaftliche Vorlesugen, 1895; Erkenntnis und Irrtum, 1905) contributed to the birth of the philosophy of science as we currently know it – albeit Mach never wanted to be called philosopher (BN/mach1886,VI). His epistemological investigations are characterized by an historical approach to the scientific enterprise, which determines an anti-metaphysically-oriented view of theories and concepts. In Beiträge zur Analyse der Empfindungen (BN/mach-1886. From the 1900 extended second edition the book is titled Die Analyse der Empfindungen und das Verhältnis des Physischen zum Psychischen), Mach deals with questions related to our relationship with both the external and the internal world, with the attempt to get both physics and * All references are made to the Digital Critical Edition of Nietzsche’s works (http://www.nietzschesource.org/#eKGWB), which will soon include also the text from Nietzsche’s private library. Any reference is the final part of an URL, which first part is http://www.nietzschesource.org/. Thus, e.g. eKGWB/JGB-15 is the reference to Nietzsche’s Beyond Good and Evil, §15, i.e. http://www.nietzschesource.org/eKGWB/JGB-15. Gori / Mach_NB 2 psychology rid of obscure metaphysical concepts, that is, concepts which refer to nonexisting entities such as the ego. The framework of the book is that of the physiology of the senses (Physiologie der Sinne) as developed in modern times. As we read in (BN/mach-1886,1) Johann Goethe, Arthur Schopenhauer and Johannes Müller are the main figures addressed. But also Gustav Fechner plays a fundamental role, for Mach explicitly aims to overcome the difficulties that Fechner’s Elemente der Psychophysik (1860) did not solve, and he tries to do it through his “principle of the complete parallelism of the psychical and physical [Princip der vollständigen Parallelismus des Psychischen und Physischen]” (BN/mach-1886,28). Mach’s attempt to re-define the relationship between the two realms of the physical and the psychical, and therefore to provide new boundaries for the scientific inquiries devoted to them, is the guiding line of his 1886 book. As a result, Mach develops an original monistic conception, according to which physical and psychical are neither two realms whose actual existence is independent from us (rejection of the traditional dualism between matter and soul/spirit and of the ordinary metaphysical realism), nor the expression of a metaphysical substance lying behind that distinction (rejection of Fechner’s form of Spinozism). For Mach, we only deal with a neutral substratum of so-called “elements”, which can be defined as the uninterpreted data, that is, the result of a “pure” relationship between ourselves and the external world. Given that we can only experience this relationship through our body (Leib), Mach calls these elements “sensations”, but he also warns us not to conceive these sensations in the ordinary empiricist sense. Our sensations are both the starting point and the actual limit of any knowledge we can be capable of, but nothing can be said about their metaphysical existence. Therefore, Mach’s neutral monism is a kind of postempiricist and anti-metaphysical positivism. The first chapter of Mach’s Beiträge zur Analyse der Empfindungen (Antimetaphysische Vorbemerkungen, BN/mach-1886,1) is the most interesting as much as theoretically dense part of the book. Here, Mach deals with his theory of the elements and critique of the traditional conception of subjectivity (Ich). He argues that our world-experience is grounded on complexes of colours, sounds, temperatures, spaces, times, etc., which “are not absolutely permanent” (BN/mach-1886,2), but that we treat as permanent, by giving names to the relatively more stable compounds (BN/mach-1886,4). This is a fundamental – as much as biologically useful – mistake, for we tend to give value to “the vague image which we have of a given permanent complex. (…) Being an image which does not perceptibly change when one or another of the component parts is taken away, [that Gori / Mach_NB 3 image] seems to be something which exists in itself” (BN/mach-1886,4, BN/mach1886,5). But that leads to the metaphysical, “monstrous [ungeheuerlich]” concept of a thing in itself, to the idea of an essence of things which exists independently from us as much as from our very relationship with those things (ibid.). With the I it happens precisely all this. The I or ego is only a “complex of memories, moods, and feelings, joined to a particular body [Körper] (the human body [Leib]), which (…) manifests itself as relatively permanent” (BN/mach-1886,3), whereas it is in fact “as little absolutely permanent as are bodies” (BN/mach-1886,3, fn. 1). For Mach both the ego and the bodies are merely theoretical “substance-concepts [Substanz-Begriffe]” elaborated for the aim of orientation, and the complexes they denote in fact “disintegrate into elements” (BN/mach1886,4). The development of scientific psychology especially demonstrated that any attempt to find a presupposed psychical unity at the basis of the thought-processes is destined to fail; or, as Mach famously remarks: “we cannot save the I [das Ich ist unrettbar]” (BN/mach-1886,18, fn. 12). More generally, Mach maintains that the development of advanced studied in science allows us to become aware of “the superfluity of the role played by the [Kantian] ‘thing in itself’” and to finally get rid of the “good dose of false metaphysics [falsche Metaphysik] (…) we necessarily absorb (…) with the valuable parts of physical theories” (BN/mach-1886,21, fn. 14). In the second chapter (Die Hauptgesichtspunkte für die Untersuchung der Sinne, BN/mach-1886,25) Mach deals with the principle of continuity, namely “the habit of connecting two things, A and B, in thought,” which determines that “wherever A appears, B is added in thought” (BN/mach-1886,25), and presents the “principle of the complete parallelism of the psychical and physical” (BN/mach-1886,28). Furthermore, in a long footnote Mach expresses his biological i.e. evolutionary viewpoint with reference to the theories of Herbert Spencer and Charles Darwin. For Mach, “a psychology in the SpencerDarwinian sense, founded upon the theory of evolution, but supported by detailed positive investigation, would yield richer results than all previous speculation has done. – These observations and reflections had long been made and written down when Schneider’s valuable work (Der thierische Wille, Leipzig 1880), which contains many that are similar, made its appearance” (BN/mach-1886,37. The last observation is especially interesting for the present entry, since Schneider’s work is collected in Nietzsche’s library: cf. BN/schneider-g-1880). The volume continues with two chapters devoted to the experience of space-perception (Die Raumempfindungen des Auges, BN/mach-1886,40 and Weitere Untersuchung der Gori / Mach_NB 4 Raumempfindungen, BN/mach-1886,55). These sections deal with more technical questions, with no immediate philosophical consequences. The fifth chapter (Beziehung der Gesichtempfindungen zu einander und zu andern psychischen Elementen, BN/mach-1886,79) is also technical, but some of the issues explored can be related to Nietzsche’s interests. Mach especially deals with the role of the intellect in managing sensations actively and creatively – something that, of course, generates metaphysical problems of some sort. For example, we read that “with the development of intelligence [Intelligenz], the parts of these complexes [of sensations] necessary to produce the excitation constantly diminish, and the sensations are more and more supplemented and replaced by the intellect, as may be daily observed in children and adolescent animals” (BN/mach-1886,80). As in the previous chapters, Mach’s primary interest is to defend his conception of knowledge and perception. His observations on how our sight works, therefore, aim to show that in every perceptive activity we unconsciously and automatically intervene by supplementing an incomplete image or by creating theoretical unities instead of chaotic (i.e. lacking points of orientation) complexes. Also in the case of sight, “it is not the elements of the complex, but the whole physiologico-optical complex that is of importance. This complex the eye seeks to fill out and supplement, according to the habits acquired (or inherited) in its environment, whenever (…) the appearance of the complex is incomplete” (BN/mach1886,86). The book continues with two chapters devoted to our perception of time and tone (Die Zeitempfindung, BN/mach-1886,103 and Die Tonempfindungen, BN/mach-1886,112). These are issues to which Mach contributed in an original way, starting from a discussion of both Hermann von Helmholtz’s and Karl Stumpf’s theories (cf. H. Helmholtz, Die Lehre von den Tonempfindungen, 1863, and K. Stumpf, Tonpsychologie, 1883). The final chapter (Einfluss der vorausgehenden Untersuchungen auf die Auffassung der Physik, BN/mach-1886,141) includes some general observations which are worth to be considered, for they offer a broader view of the issues addressed in the book and provide the basis for Mach’s further work in epistemology. For Mach, his research would help to “remove a very widespread prejudice and, with it, a barrier” (BN/mach-1886,141); this prejudice is precisely the idea that “there is [a] rift between the psychical and the physical, inside and outside,” that there are “‘sensation[s]’ to which an external ‘thing’, different from sensation, correspond” (BN/mach-1886,141). But there is nothing of that sort. On the contrary, “there is but one kind of elements, out of which this supposed inside and Gori / Mach_NB 5 outside are formed – elements which are themselves inside or outside, according to the aspect in which, from the time being, they are viewed” (BN/mach-1886,141). In claiming this, Mach contrasts the traditional view his fellow physicists uncritically accepted – and he maybe goes too far! The post-empiricism he defends is in fact a sort of pragmaticallyoriented “sensualism without metaphysics”, given that, for Mach, “the boundary-line between the physical and the psychical is solely practical and conventional [praktische und conventionelle]” (BN/mach-1886,142) and, therefore, theories and concepts have a mere instrumental value. But Mach’s concern with traditional metaphysical realism led him to the firm rejection of the very existence of atoms and molecules (something that, it must be said, was still debated at his time). According to him, “if ordinary ‘matter’ must be regarded merely as a highly natural, unconsciously constructed mental symbol for a relatively stable complex of sensation elements, much more must this be the case with the artificial hypothetical atoms and molecules of physics and chemistry. The value of these implements for their special, limited purposes is not one whit destroyed. As before, they remain economical ways of symbolizing experience. But we have as little right to expect from them, and certainly not more enlightenment and revelation than from experience itself. We are on our guard now, even in the province of physics, against overestimating the value of our symbols. Still less, therefore, will the monstrous idea of employing atoms to explain psychical processes ever get possession of us; seeing that atoms are but the symbols of those peculiar complexes of sensational elements which we meet with in the narrow domains of physics” (BN/mach-1886,142, BN/mach-1886,143). As Mach affirms at the end of the first chapter of the essay (BN/mach-1886,24), he is not interested in discrediting “the standpoint of the plain man,” but only to show that, at some point and for some determined purposes, “we are obliged to abandon it.” His antimetaphysical attempt is therefore an attempt to enlighten the mind of his fellow scientists (cf. the preface to his Mechanik) and show them that the value of the concept they daily use must be reconceived. These concepts are quite useful economical symbols, and there is no need to obliterate them from the scientific enterprise. But the fruitfulness and operational efficacy of these “thought symbols [Gedankensymbol]” (BN/mach1886,8) is no proof of the actual existence of the objects they denote. Science, therefore, should get rid of these substance-concepts, or at least accept that, out of a well-defined semantic boundary, these concepts have no meaning – and, consequently, they only create confusion and metaphysical obscurities (cf. BN/mach-1886,20). Gori / Mach_NB 6 2. Nietzsche’s reading marks. Similarities between Nietzsche’s and Mach’s views The book contains two reading marks: in (BN/mach-1886,61) Nietzsche corrects a typo, and in (BN/mach-1886,85) he underlines a sentence. This shows us that Nietzsche gave more than a cursory look at the book, but of course one cannot infer that he read it carefully. Nevertheless, Nietzsche’s reading marks in (BN/mach-1886,85) are a good starting point for a brief exploration of the most interesting parallelisms between Nietzsche and Mach. The passage Nietzsche seems to be interested in deals with Johannes Müller’s description of sight-phantasms as explored in Über die phantastischen Gesichtserscheinungen (1826). For Mach, those are “are independent phenomena, essentially connected with the sense-organs, and characterized by complete visual objectivity. They are veritable [wahre] imagination- and memory-phenomena of the senses” (BN/mach-1886,83). In Nietzsche’s writings there seems to be no reference to that issue, but Müller was known to him, at least through Friedrich Lange’s Geschichte der Materialismus (BN/lange-f1887). In the second volume of this book, Lange devoted a chapter to The Physiology of Sense Organs and the World of Representation (BN/lange-f-1887,712. The chapter is already included in the 1875 extended second edition, also read by Nietzsche). In that section, Lange famously holds that “the physiology of sense organs is developed or corrected Kantianism” (BN/lange-f-1887,713) and deals with the studies of Hermann von Helmholtz and Johannes Müller. Lange does not take into account the book Mach refers to; he rather quotes Müller’s 1826 essay Zur vergleichenden Physiologie des Gesichtssinnes des Menschen und der Thiere (Leipzig: K. Knobloch) where, as we read in (BN/lange-f-1887,716), “Müller pointed out that the image of our own body is perceived under entirely the same conditions as the image of external objects”; consequently, our own body is “a mere scheme of representation, a product of our optical apparatus”. These observations lead us to (eKGWB/JGB-15), where Nietzsche apparently develops and discusses Lange’s remark (“What? and other people even say that the external world is the product of our organs? But then our body, as a piece of this external world, would really be the product of our organs! But then our organs themselves would really be – the product of our organs!”). This is an important as much as discussed passage, which is not my intention to further deal with, here. What is interesting, for the aim of the present research, is the path leading from Müller to Beyond Good and Evil (via Gori / Mach_NB 7 Lange), for Nietzsche’s 1886 book contains a couple of interesting correspondences with Mach’s view – actually, with Mach’s Beiträge zur Analyse der Empfindungen. The most important parallelism concerns Nietzsche’s critique to the concept of subject (I, ego, soul). In (eKGWB/JGB-12), Nietzsche argues that “materialistic atomism (…) is one of the most well-refuted things in existence” and that “we must put an end to that other and more disastrous atomism, (…) the atomism of the soul [Seelen-Atomistik]. Let this expression signify the belief that the soul is something indestructible, eternal, indivisible [Untheilbares], that it is a monad, an atomon: this belief must be thrown out of science!”. Furthermore, in (eKGWB/JGB-16 and eKGWB/JGB-17), Nietzsche rejects the ordinary (Cartesian) belief that the proposition “I think” is an immediate certainty. “In place of that ‘immediate certainty’ – observes Nietzsche – the philosopher gets handed a whole assortment of metaphysical questions, genuinely probing intellectual questions of conscience, such as: ‘Where do I get the concept of thinking from? Why do I believe in causes and effects? What gives me the right to speak about an I, and, for that matter, about an I as cause, and, finally, about an I as the cause of thoughts?’” (eKGWB/JGB-16). Finally, Nietzsche insists that “a thought comes when ‘it’ wants, and not when ‘I’ want. It is, therefore, a falsification of the facts to say that the subject ‘I’ is the condition of the predicate ‘think’” (eKGWB/JGB-17). It would be much more appropriate to say “it thinks” (Es denkt), as suggested by Georg Christoph Lichtenberg, but for Nietzsche “there is already too much packed into the ‘it thinks’: even the ‘it’ contains an interpretation of the process, and does not belong to the process itself” (eKGWB/JGB-17). The metaphysical need which imbues our grammatical habits forces us to look for a source of the thought activity separated from the activity itself. But that also happens in the case of the physical world-description, as modern scientists critically remarked. Thus, Nietzsche conclusively argues that, “following the same basic scheme, the older atomism looked behind every ‘force’ that produces effects for that little lump of matter in which the force resides, and out of which the effects are produced, which is to say: the atom. More rigorous minds finally learned how to make do without that bit of ‘residual earth,’ and perhaps one day even logicians will get used to making do without this little ‘it’ (into which the honest old I has disappeared)” (eKGWB/JGB-17). It is impressive to see that quite similar remarks can be found in Mach’s 1886 essay. In an important footnote from the first chapter (BN/mach-1886,18 and BN/mach-1886,19, fn. 13), Mach criticizes “the habit of treating the unanalysed ego-complex as an indiscerptible unity [untheilbare Einheit]” in science and argues that it is impossible to Gori / Mach_NB 8 find an actual “seat of the soul [Sitz der Seele]”, for there is nothing of the sort into the human brain. Furthermore, in the following page (BN/mach-1886,20) Mach observes that we should give fully assent to Lichtenberg’s conclusion that “we should say it thinks just as we say it lightens. It is going too far to say cogito, if we translate cogito by I think. The assumption, or postulation, of the ego is a mere practical necessity”. Now, it would be easy to argue that Nietzsche has been influenced directly by Mach, if only Beyond Good and Evil would not have been written before the publication of the Beiträge zur Analyse der Empfindungen! But in fact an exposition of the most recent developments of scientific psychology as much as Lichtenberg’s anti-cartesianism can be found in Lange’s Geschichte der Materialismus (cf. e.g. the chapters on Brain and Soul and Scientific psychology from the second volume of that book, BN/lange-f-1887,511 and BN/lange-f1887,550 respectively; as for the rejection of the ordinary belief in a causally-efficacious subject of brain activity, cf. BN/lange-f-1887,190). Furthermore, Lichtenberg’s view was also directly known by Nietzsche, who in his personal copy of Lichtenberg’s Vermischten Schriften (BN/Lichtenberg-1867a,99) marked the passage quoted by both Lange and Mach. Thus, the parallelism between Nietzsche and Mach can be explained by the fact that they developed their views starting from shared sources (directly or indirectly addressed). Anyway, it is striking to see that the same ideas are expressed in both Nietzsche and Mach in the same order, with Lichtenberg’s remark making its appearance just after the rejection of the metaphysical idea of an I or soul as cause of thoughts. It is also worth to note that Nietzsche’s general aim to get rid of the prejudices (Vorurtheilen) of his fellow philosophers (eKGWB/JGB, Book I) through an antimetaphysical reflection on the fundamental issues of Western though closely resembles Mach’s attempt to enlighten the mind of modern scientists and remove “a very widespread prejudice [ein sehr verbreitetes Vorurtheil]” which only complicates the interpretation of both physical and psychical events (see BN/mach-1886,141). As shown above, this prejudice holds that a “permanent nucleus” can be found as origin of any physical or psychical process, something “unconditionally constant” whose existence is independent from that activity itself (cf. BN/mach-1886,8, BN/mach-1886,154 and BN/mach1886,155). For Mach, this is pure illusion, for the substance-concepts “matter”, “body”, “ego”, “atom”, etc. are only thought symbols elaborated for practical purposes. Nietzsche’s critique of the philosopher’s ordinary prejudices leads us to Twilight of the Idols, another work where it is possible to find parallelisms with Mach’s Beiträge zur Analyse der Empfindungen, but which has been written after the publication of Mach’s Gori / Mach_NB 9 1886 essay. In Twilight of the Idols Nietzsche in fact attempts to make the eternal idols i.e. old truths disappear by showing their metaphysical inconsistency, and he grounds his critical remarks towards Western philosophy on some observations already presented in Beyond Good and Evil. Among them, we find the idea that the I is only “a fairy tale, a fiction, a play on words” (eKGWB/GD-Irrthuemer-3), that is, any belief in its existence as a substance-concept with causal efficacy is not admitted anymore (cf. also eKGWB/GD-Vernunft-5). But Nietzsche talks also of the role of the senses, and in a still widely debated paragraph argues that “the senses do not lie [lügen] the way the Eleatics thought they did, or the way Heraclitus thought they did, – they do not lie at all [sie lügen überhaupt nicht]. What we do with the testimony of the senses, that is where the lies begin, like the lie of unity, the lie of objectification, of substance, of permanence… ‘Reason’ makes us falsify the testimony of the senses. The senses are not lying when they show becoming, passing away, and change [Sofern die Sinne das Werden, das Vergehn, den Wechsel zeigen, lügen sie nicht]” (eKGWB/GD-Vernunft-2). Most of the interpretive problems with this passage rest in the word “lügen”, which is morally-laden. But in a preparatory note we read: “Die Sinne sind es nicht, die Täuschen” (eKGWB/NF1888,14[134], my emphasis). Similarly, in (BN/mach-1886,8, fn. 2), Mach affirms that “the expression ‘sense-illusion’ [Sinnestäuschung] proves that we are not yet fully conscious, or at least have not yet deemed it necessary to incorporate the fact into our ordinary language, that the senses represent things neither wrongly nor correctly [die Sinne weder falsch noch richtig zeigen]. All that can be truly said of the sense-organs is that under different circumstances they produce different sensations and perceptions”. Thus, Nietzsche’s view on that issue seems to be consistent with Mach’s. Furthermore, the way the activity of sense organ is outlined in the Beiträge zur Analyse der Empfindungen helps us to shed light on Nietzsche’s statement and, consequently, not to overinterpret a conception which is apparently only a neutral view of the physiological processes occurring before a moral interpretation takes place. Another aspect of striking semantic as much as argumentative similarity concerns the nietzschean obliteration of the very dichotomy between the “apparent” and the “true” world. In the section devoted to the history of that “error”, Nietzsche discards as “unattainable, unprovable and unpromisable [unerreichbar, unbeweisbar, unversprechbar]” the world of substance-concepts, and finally argues that along with the “true” world we also “get rid of the illusory [scheinbare] one” (eKGWB/GD-Welt-Fabel). But this is something that follows from Mach’s “monistische Standpunkt”, too (BN/mach- Gori / Mach_NB 10 1886,10). In fact, Mach argues that, once we accept that “the supposed unities ‘body’ and ‘ego’ are only makeshifts, designed for provisional orientation and for definite practical ends, (…) we find ourselves obliged, in many more advanced scientific investigations, to abandon them as insufficient and inappropriate [unzureichend und unzutreffend]. The antitheses between ego and world, between sensation or appearance and thing, then vanishes [der Gegensatz zwischen Ich und Welt, Empfindung oder Erscheinung und Ding fällt dann weg], and we have simply to deal with the connection of the elements (…) of which the antithesis was only a partially appropriate and imperfect expression” (BN/mach-1886,9, BN/mach-1886,10, my emphasis). The progress of scientific inquiries lies precisely on this, for Mach: “Science has simply to accept this connection, and to get its bearings in it, without at once wanting to explain its existence” (BN/mach-1886,10). Finally, another interesting parallelism can be encountered between Twilight of the Idols and Mach’s 1886 essay. In (eKGWB/GD-Irrthuemer-4) Nietzsche deals with “the error of imaginary causes” and makes the example of the sensory experience in dreams: “We experience a certain sensation (following the sound of cannon fire in the distance, for example) and then retrospectively supply a cause for it (which often takes the form of a whole little novel with the dreamer as the protagonist). Meanwhile, the sensation remains in a type of resonance: it waits, as it were, until our causal instinct allows it to come into the foreground (…). The cannon fire takes place inside a causal nexus, in what seems like a temporal reversal [Umkehrung der Zeit]. The later event, the motivation, is experienced first, often with hundreds of details that flash past, followed by the shot… What has happened? The idea that were created by a certain physical condition were mistaken for the cause of that condition”. Similarly, in the chapter devoted to the sensation of time, Mach presents the following experience: “I have repeatedly observed an interesting phenomenon which should be cited here. I have been sitting in my room, absorbed in work, while in an adjacent room experiments in explosions were being carried on. It regularly occurred that I shrank back startled, before I heard the report. Since the attention is especially inert in dreams, naturally the most peculiar anachronisms occur in this state, as everyone has doubtless observed. For instance, we dream of a man who rushes at us and shoots, awake suddenly, and perceive the object which, by its fall, has produced the entire dream. Now there is nothing absurd in assuming that the acoustic stimulus enters simultaneously different nerve-tracks and is met there by the attention in some inverted order [verkehrter Ordnung], just as, in the case above mentioned, I perceived first the general excitation and afterwards the report of the explosion. But in many cases it is Gori / Mach_NB 11 undoubtedly a sufficient explanation to assume the interweaving of sensation with the framework of a dream already present” (BN/mach-1886,107, BN/mach-1886,108). The two passages are quite similar, indeed, and one could be tempted to argue that Nietzsche is indebted to Mach, on this particular issue. Unfortunately, in Human, all too Human I, 13 Nietzsche already dealt with that topic, and reflections on the time-inversion (ZeitUmkehrung) can be also found in his 1884-85 notebooks (cf. e.g. eKGWB/NF1884,26[35] and eKGWB/NF-1885,34[54]). Therefore, in this case (and, accordingly, we shall remain sceptic about the others, too), Mach’s Beiträge zur Analyse der Empfindungen cannot be considered a direct source, but only the signal of research interests that Nietzsche and Mach had in common, as much as of a shared framework which involves studies on the physiology of the sense organs. 3. Literature on the topic The similarities and possible connections between Nietzsche and Mach have been studies during the last decades. Nadeem Hussain devoted two papers to the topic, where he especially provides a Machian interpretation of JGB 15: Nadeem Hussain, “Nietzsche’s Positivism” in: European Journal of Philosophy, 12 (3), 2004, pp. 326-368. Nadeem Hussain, “Reading Nietzsche Through Ernst Mach”, in: Nietzsche and Science, ed. by Thomas Brobjer and Gregory Moore, Ashgate: Aldershot, 2005, pp. 111-129. Thorough studies on Nietzsche and Mach, with a particular focus on their post-positivist (anti-metaphysical) approach to both knowledge and subjectivity, have been provided by Pietro Gori, e.g. Pietro Gori, “The Usefulness of Substances. Knowledge, Metaphysics and Science in Nietzsche and Mach”, in: Nietzsche-Studien, 38, 2009, p. 111-155. Pietro Gori, Il meccanicismo metafisico. Scienza, filosofia e storia in Nietzsche e Mach, Bologna: Il Mulino, 2009. Pietro Gori, “Psychology without a Soul, Philosophy without an I. Nietzsche and 19th century Psychophysics (Fechner, Lange, Mach)”, in: Nietzsche and the Problem of Subjectivity, ed. by João Constâncio et alia, Berlin: De Gruyter, p. 166-195. Gori / Mach_NB 12 Pietro Gori, Nietzsche’s Pragmatism. A Study on Perspectival Thought, eng. trans. Berlin/Boston: De Gruyter, 2019 (forthcoming). On Nietzsche’s interest in the physiology of sense organs, also with reference to Mach, see e.g. Sören Reuter, “Nietzsche und die Sinnesphysiologie und Erkenntniskritik” in: Handbuch Nietzsche und die Wissenschaften, ed. by Helmut Heit and Lisa Heller, Berlin/Boston: De Gruyter 2014, p. 79-106. Christian Emden, Nietzsche’s Naturalism: Philosophy and the Life Sciences in the Nineteenth Century, Cambridge: Cambridge University Press, 2014. On Nietzsche’s anti-cartesianism and the critique of the metaphysical concept of subjectivity in JGB, see also Nikolaos Loukidelis, „Es denkt“: Ein Kommentar zum Aphorismus 17 aus ,Jenseits von Gut Böse’, Königshausen und Neumann, 2013. The issue of time-inversion is explored in Luca Lupo, Le colombe dello scettico. Riflessioni di Nietzsche sulla coscienza negli anni 1880-1888, Pisa: ETS, 2006 (in particular, pp. 42-54). On Mach’s neutral monism, his original empiricism, and his cultural framework, see e.g. Friedrich Stadler (ed.), Ernst Mach – Life, Work, Influence (Vienna Circle Institute yearbook, 22): Heidelberg: Springer, 2018. John Blackmore, Ryoichi Itagaki and Setsuko Tanaka (eds.), Ernst Mach's Vienna 1895-1930. Or Phenomenalism as Philosophy of Science, Dordrecht: Kluwer, 2001. Robert Cohen and Raymond Seeger (eds.), Ernst Mach: Physicist and Philosopher, Dordrecht: Kluwer, 1970. Erik Banks, Ernst Mach’s World Elements. A Study in Natural Philosophy, Dordrecht: Kluwer, 2003. Erik Banks, The Realistic Empiricism of Mach, James, and Russell: Neutral Monism Reconceived, Cambridge: Cambridge University Press, 2014. Pietro Gori, “Ernst Mach’s Pragmatic Realism”, in: Revista Portuguesa de Filosofia, 74, 2018, pp. 151-172. Gori / Mach_NB 13 The translations adopted in this entry are the following: Friedrich A. Lange, History of Materialism and Criticism of its Present Importance, eng. trans. in 3 voll., Boston: Houghton, Mifflin & c., 1877-1881. Ernst Mach, The Analysis of Sensations and the Relation of the Physical to the Psychical, Chicago/London: Open Court, 1914. Friedrich Nietzsche, Beyond Good and Evil, eng. trans. Cambridge: Cambridge University Press, 2002. Friedrich Nietzsche, The Anti-Christ, Ecce Homo, Twilight of the Idols, and Other Writings, eng. trans. Cambridge: Cambridge University Press, 2005. Gori / Mach_NB 14 [B] E. Mach und P. Salcher, “Photographische Fixirung der durch Projectile in der Luft eingeleiteten Vorgänge”, in: Repertorium der Physik, ed. F. Exner, 1887, pp. 587-599 Abstract: In this 1887 report, Ernst Mach and Peter Salcher published the result of a series of ballistic experiments they performed, which revealed an essential difference between flight at a subsonic and supersonic velocities. The paper is the first step for the explanation of physical events such as the sonic bang produced by objects that exceed the speed of sound. Keywords: Shock waves, Supersonic aerodynamics, Ballistic 1. The study of shock waves In 1887, after having bought and read (although not thoroughly) Ernst Mach’s Beiträge zur Analyse der Empfindungen (BN/mach-1886), Nietzsche asked the editor Naumann to send a copy of his Zur Genealogie der Moral to Mach (Nietzsche to Naumann, 8 November 1887, eKGWB/BVN-1887,946). In return, Mach sent Nietzsche a copy of an important study on the shock waves produced by supersonic projectiles which he carried out with the help of Peter Salcher (professor of physics at the Royal Austrian Naval Academy). The paper collected in Nietzsche’s library contains a dedication on the front matter (“Herrn Prof. Dr. Nietzsche hochachtungsvoll, EM.”; BN/mach), but no reading marks. This must not surprise, for the text is quite technical and does not deal with philosophical issues of any sort. Mach and Salcher’s paper is the result of a series of unique ballistic experiments they performed since 1886 (incidentally, the experimental techniques necessary to perform these investigations have been developed by Mach himself). The observations they made revealed an essential difference between flight at a subsonic and supersonic velocities, namely that a projectile exceeding the speed of sound produces a hyperbolic-like head wave (front) and a tail wave (rear), both similar to a bow wave (cf. fig. 5 in BN/mach,596 and fig. 7 in BN/mach,598). The study most probably originated from Mach’s interest in acoustic and the experiments on the phenomena of refraction and reflection of sound waves he performed earlier. As a development of this inquiry, Mach and Salcher Gori / Mach_NB 15 succeeded in making visible something that, before them, was only deducible in theory, namely the aerodynamical phenomena associated with flying projectiles. This made further theoretical investigations possible, but it also allowed to explain events observed previously and not experimentally repeatable, such as those related to the fall of a meteor into the atmosphere. In fact, a meteor falling down to the surface of the earth produces first a sharp bang, and only thereafter one hears the noise of the impact. But this bang is nothing else than the bow shock reported by Mach, since the meteor comes down through the atmosphere with supersonic velocity. This physical effect is nowadays observable in the case of supersonic jets, which at the speed of Mach 1 (i.e. approaching the speed of sound; Mach number [M] is in fact defined as the ratio of [u] the local flow velocity with respect to the boundaries to [c] the speed of sound in that particular medium: M = u/c) produces a sonic bang and a vapor cone, accordingly to what Mach and Salcher first reported in their 1887 paper. In fact, during the experiments that he performed, Salcher noticed a series of intermediate waves (later called “Mach lines”), which are small shock wave projected at an angle dependent on the speed of the air in the tunnel. Mach’s conclusion, when he interpreted the collected data and the photos taken by Salcher (cf. BN/mach,600), was that the velocity v of a supersonic projectile can be determined from the head wave cone geometry by the relation sin α = co/v = 1/M where co is the sound velocity in the ambient gas at rest, α is the half-cone angle, and M is the Mach number (later, this equation was called Mach equation, the cone geometry Mach cone and the cone angle Mach angle). The importance of this paper rests almost exclusively on the way Mach and Salcher contributed to the progress of experimental researches on both the shock and the sound waves. However, it also outlines a multifaceted image of Mach, whose role in the history of the philosophy of science must not be underestimated. Although he was basically an experimental physicist, his reflections on the development of ideas and theories as much as his attempt to get science rid of metaphysical obscurities deeply inspired the early nineteenth-century scientific philosophy (not to mention the Logical Empiricism movement, which arose a few decades later). These reflections are based on his experimentalism and especially on the idea that theoretical and empirical research are intertwined; that is to say, ideas must be supported by observative facts, in order not to lead to ill-funded as much as illusory conclusions. This is particularly important in the case of unobservable entities whose occurrence can only be detected indirectly (a Gori / Mach_NB 16 fundamental issue in current philosophy of science). The possibility of making visible at least the events these presupposed entities are involved in is in fact crucial, in order to develop a well-funded theory about them and try to avoid unnecessary and, most of the times, detrimental metaphysical commitments. Mach’s interest in sound/shock waves falls within this general picture. In fact, Mach mentioned his studies on ballistic in his less technical publications (se e.g. the lecture Über Erscheinungen an fliegenden Projectilen added to the 1903 third edition of Mach’s Populär Wissenschaftliche Vorlesungen), which aimed to popularize physical studies and cultivate an enlightened culture that could take care of the role played by epistemology in the more advanced scientific studies as much as in philosophical speculations. 1. Literature Christoph Hoffmann and Peter Berz (eds.), Über Schall. Ernst Machs und Peter Salchers Geschloßfotografien, Göttingen: Wallstein, 2001. Peter O.K. Krehl, History of Shock Waves, Explosions and Impact. A Chronological and Biographical Reference, Heidelberg: Springer, 2009. Ernst Mach, Populär Wissenschaftliche Vorlesungen, Leipzig: Barth 19033. Raymond J. Seeger, “On Mach’s Curiosity About Shockwaves”, in: Robert Cohen and Raymond Seeger (eds.), Ernst Mach: Physicist and Philosopher, Dordrecht: Kluwer, 1970, pp. 60-68. Friedrich Stadler, Vom Positivismus Zur „Wissenschaftlichen Weltauffassung“ Am Beispiel der Wirkungsgeschichte von Ernst Mach in Österreich von 1895 bis 1934, München: Löcker, 1982. Wolfgang F. Merzkirch, “Mach’s Contribution to the Development of Gas Dynamics”, in: Robert Cohen and Raymond Seeger (eds.), Ernst Mach: Physicist and Philosopher, Dordrecht: Kluwer, 1970, pp. 42-59.