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Mach’s Philosophy: Sensation, Matter, Soul

Manuscript notes for his 1872 lectures on the principal problems in physics show that Mach began by arguing that sensation is a general property of matter. If it is not regarded as an emergent property of groups of molecules, then it has to be considered part of the elements themselves. Mach then asked where the soul is located. Experiments with animals showed it couldn’t be located in the brain: the soul isn’t so simple, he said, exploring an analogy with the state, which he commented “looks like a person.” Mach asked his students to consider Bismarck’s soul before moving between the soul of the professions, individuals and back to the state (Mach 1872). Five years after the Prussian defeat of Austria and shortly after Bismarck had been made Imperial Chancellor of a newly unified Germany, Mach’s questions made an abstract point about parts and wholes with direct political meaning, without at any point stating his own political stance. Nevertheless it is likely that Mach’s politics was important to many of his readers, both attracting some readers, like those in the socialist circles around Einstein as a student in Zurich, and repelling others, like Max Planck (Feuer 1974, 11-22; Heilbron 2000, 44-60).

In this particular instance Mach’s underlying philosophical point was that we attribute souls to others by adding them in thought, by analogy with our direct experience of our own outer and inner sides. Scientific concepts are no different. When he asked his assistant Hajek to bring a prism into the room, one could understand Hajek as an automaton, but that was much more difficult than ascribing him a soul; just as potential theory or Ampere’s rules had a practical economical value. Mach’s course was dedicated to overcoming the cleft between the physical and the psychic. He finished his introductory lecture with striking methodological advice, which is bold in its epistemological and ontological parity and deliberately philosophical, humdrum and poetic at once. He told his students:

So in fact we can hope to come to a better understanding of the world if we measure ourselves with the standards of the outer world and the outer world with our own standards,

considering it as physical process, but attributing sensation to matter (Mach 1872).

This kind of comparative inversion may seem a long way from what we know about Mach’s attack on Newtonian absolutes, but in fact I think there’s an interesting practical pathway from his methodological advice to the critique of Newton’s bucket that Mach offered in 1883. Further, considering that critique alongside the physiological and psychological perspective that Mach described in his 1886 book on sensations, will show strong relations between Mach’s thought on the outer and inner worlds.

An important illustration of Mach’s methodology comes in his work on the physics and physiology of our sense of balance and the vertical. This was stimulated by unusual experiences while travelling on a train in 1873, which led Mach to conduct experiments on our sensory experience of rotation, but also of fall. To do so, Mach built a rotating frame, as well as a see-saw device and an inclined plane, and he experimented extensively on the different factors leading to our bodily awareness of motion in such circumstances. Before writing extensively on Galileo’s and Newton’s contributions to mechanics in 1883, then, Mach had himself experienced the controlled fall of trundling down an inclined plane in a trolley, or being swung up and down, and he had sat in a chair spinning on a central axis like a bucket on a string, or rotating like a child on a merry-go-round or train-traveller going around a curve. Paying close attention to distinguishing the role of the head, muscles, skin and the visual system in such motions and experimenting with pigeons and rabbits as well as himself, Mach established firstly that we perceive the resultant of centrifugal and gravitational forces as vertical. Secondly, he made the physiological discovery that the motion of the fluids in the inner ear provides a physical, mechanical system that allows our nerves to register the vertical and changes in orientation, and he showed that the nerves accommodated to constant forces but reacted to changes in them to give a sensitive perception of rotation (Mach 1875; Staley 2013). Mach was quite literally bringing the measures of the outer world into play in order to analyse our sense of motion.

There are some interesting reflections of this physiological research in Mach’s later work on mechanics, but they are often somewhat indirect. Interleaved into his notes for his 1880 lecture course on mechanics is a brief note that our own body is indispensible in establishing the laws of mechanics (Mach 1880). His 1873 laboratory notebook shows that his research on rotation and fall led Mach to return to the history of mechanics with the intention of discussing “Newton, once more,” (Mach 1873b) but in fact his first sustained new thoughts on Newton seem to have come in 1879, when he discussed the Newtonian epoch and drew a diagram that seems to prefigure his 1883 discussion of Newton’s bucket (Fig. 6.2).

Remember that in 1872 Mach had discussed Foucault’s pendulum and the bulging of the earth at the equator when critiquing Newton’s recourse to absolute motion. Now he seems to have narrowed his analysis down to the particular example that Newton had offered, of a spinning bucket with its water, before shifting scale in a speculative indication of the difficulties of understanding how to approach the phenomena if the bucket’s walls were to be expanded dramatically. In this diagram he notes first that it makes no sense to assume absolute space, and then that there can be no talk of the relative motion of the inner cylinders alone, because of the existence

This sketch of relative rotation anticipates Mach’s published discussion of Newton’s bucket experiment. Deutsches Museum, Munich, Archives (Mach 1879)

Fig. 6.2 This sketch of relative rotation anticipates Mach’s published discussion of Newton’s bucket experiment. Deutsches Museum, Munich, Archives (Mach 1879)

of the outer ring - presumably representing the fixed stars (Mach 1879). In 1883 he was to write “No one is competent to say how the experiment would turn out if the sides of the vessel increased in thickness and in mass till they were several leagues thick” (Mach 1883, 216-17). Here I want to note that Mach’s critical thought and researches on rotation had moved from the cosmic scale of the universe to the more ordinary and intimate scale of the body and the inner ear as well as that of the bucket. It had traversed both physics and physiology.

But there was a psychological correlate to this shift in scale and move between the universe and the body, which becomes visible when Mach’s approach to mass is compared with his understanding of the ego.

Mach’s 1879 notes on rotation and mechanics are interrupted by passages on politics and psychology; and perhaps all of these were interrelated. One conjunction raises the possibility that Mach observed the methodological principle he urged on his students, to explore the inner world with the measures of the outer world and the outer world with those of the inner. At the very least it will suggest that Mach recognized conceptual similarities between physical and psychological conditions. Between a series of notes devoted first to action and reaction, inertia, pressure and counter-pressure, and then to siphons, Foucault’s pendulum and gyroscopes, Mach wrote: “Personal impersonal. The personal lies in strong connections. The person has only apparent unity. No boundaries. Renunciation of egotism. The person is an illusion. Ethical improvement.—What one now does unconsciously one will then do consciously” (Mach 1879). Just as Mach insisted you had to consider the distant stars when understanding the centrifugal forces that result in Newton’s bucket, he dissolved the boundaries between the person and the world.

This sketch illustrates the view through one eye; Mach commented that identity came “more through the environment, than through psychic identity.” Deutsches Museum, Munich, Archives (Mach 1882)

Fig. 6.3 This sketch illustrates the view through one eye; Mach commented that identity came “more through the environment, than through psychic identity.” Deutsches Museum, Munich, Archives (Mach 1882)

These comments have a very psychological cast, but there was a more physiologically oriented version of the point too, which is illustrated by a sketch Mach made in a later notebook, showing the view of his own body and his study as he sits with one eye closed (Fig. 6.3). His caption reads “The continuity of familiar stimuli. Identity more through the environment than through psychic identity” (Mach 1882). Mach believed neither the masses of the universe nor human bodies nor the self could be correctly understood without recognizing their relations to the environment, which in each case played a greater role in their formation than was commonly appreciated.

My intention here has been to identify significant interrelations between different aspects of Mach’s thought, without investigating either where they came from or the extent to which they were taken up by others (or neglected). Yet while some elements of the inclusive understanding I have offered are reflected in the historian John Blackmore’s early biography, and are pursued in Erik Banks’s comprehensive study of Mach’s philosophy, this kind of developmental picture of the relations between Mach’s philosophy and his research has been hard to perceive. One reason is probably that philosophical attention has focused on economy and not on Mach’s views about the common role of abstraction across all thought, and has neglected his methodological readiness to move between the inner and the outer. I think another reason comes down to the way Mach often presented his work. Ironically, this reflects his view about transgressing the subject boundaries of the specialist. Mach crossed such boundaries more rigorously than most scientists in this period and often emphasized the need to go beyond them, but he also thought in terms of them. Both considering as he did the different subject matters of physics, physiology and psychology, and addressing the diverse audiences of physicists, physiologists, biologists, and others, Mach was determined to reform each subject through the concerns of the other two. He always did so with a comprehensive and consistent perspective on their interrelations, but often treated these abstractly enough for his readers to miss just how intimately engaged they were in his own thought. His two major early books provide revealing illustrations of what I mean.

Mach’s 1883 book on the development of mechanics begins with a discussion of the principle of the lever. Just when you think he might have finished a rather simple example of the balance, he observes that we commonly forget it relies on several assumptions. When a beam supported at its midpoint has two equal weights suspended at equal distances, they will be in equilibrium. But to be complete, Mach writes, we might note negatively that different colors on the arms, the position of the observer, nearby processes, and etc., can all be neglected (Mach 1883, 9). It is revealing that Mach prompts us to remember that we have chosen to neglect color and the observer. His book emphasized what we neglect when we focus on mechanics, and he often stressed the need to know when the observer is irrelevant or not, but its principal subject was the physics of phenomena and not those cases where physical, physiological and psychological aspects met. Thus Mach’s physiological studies of the perception of motion went largely unremarked in 1883, though aspects of his experiments on fall found a place in a discussion of action and reaction that is the most proximate source for Einstein’s happiest thought, and the attentive reader would come across a footnote stating that Mach would not discuss the physiological nature of time and space sensations, even as he embarked on his critique of absolute time and space (Staley 2013).

When Mach addressed the physiology and psychology of sensation in his 1886 Contributions to the Analysis of the Sensations he offered a worked up version of the drawing of the world seen through one eye that he had sketched as early as 1882. Now Mach used it in the context of a discussion of the relations between our bodies and other peoples’ bodies, and of the domains of physiology, psychology, and physics, noting that the first two came into play when the phenomena at issue passed through the skin, so to speak. But this image also formed an introduction to Mach’s discussion of the ego and the world, where Mach noted how useful our ordinary conception of the ego is, but also that the researcher should go further, to recognize that the ego is not definite, unalterable or sharply bounded. Mach cited an accord with Weismann’s cell theory in arguing that continuity alone is important, and famously he concluded that the ego is unsavable (Mach 1897, 20).

For Mach, the boundaries between disciplines and between self and world are not fixed, and inertial masses, human bodies and selves are all more intimately related to the rest of the universe than is usually recognized. His insistence on this point in considering the ego was as radical as it was in considering the law of inertia; and both of these arguments stemmed from a common approach to the sciences. They should be considered alongside each other too. Doing so will change our understanding of Mach, but it may also give us new perspectives on the disciplines to which he contributed. The extent to which both contemporaries and later historians and philosophers have highlighted Mach’s anti-metaphysical arguments sometimes seems to have obscured the significance of the philosophical means that Mach offered for approaching different disciplines within the same framework, as well as the methodological means he provided to pursue interrelated concerns at the same time. We need to understand why these elements were difficult to perceive, in charting the extent to which they were taken up, combatted or neglected. For example, Mitchell Ash’s study of the origins of Gestalt psychology indicates particularly complex interrelations between the subject matter, methods and philosophical impetus that Mach’s work provided for figures such as G.E. Muller and Wolfgang Kohler (Ash 1995). Similarly, perhaps Mach’s thoughts on the ego could have served a fruitful function in the development of the philosophy of mind had they been pursued more fully, just as Heidelberger and Banks have indicated that his functional approach and neutral monism are pertinent to ongoing concerns in the study of consciousness (Heidelberg 2010; Banks 2010).

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