By Dennis Leri

Science can find no individual enjoyment in Nature; science can find no aim in Nature; science can find no creativity in Nature; it finds mere rules of succession. These negations are true of natural science. They are inherent in its methodology. The reason for this blindness of physical science lies in the fact that such science only deals with half the evidence provided by human experience.
–– A. N. Whitehead, Nature & Life[1]

…the world is darkening. The essential episodes of this darkening are: flight of the gods, the destruction of the earth, the standardization of man, the pre-eminence of the mediocre.
–– M. Heidegger, An Introduction to Metaphysics[2]

Can you see that there is no difficulty in moving the head and the arms at different rates, or moving the head at a different rate from the arms. The difficulty is to know how many movements you do… if you don’t think that is important to realize… then we have been wasting all these months of work.

Because as soon a you can do it, as soon as the pattern [of knowing how many movements you do] becomes familiar, then… you can see some wiring-in that was never moved away is gone and the effect of that is something that no money and no other happiness can [make] happen. It’s the brightest thing that you can see. Some of the people who saw lights like that, always describe it as light, bright light. Hope is a bright light. Everybody, from Francis de Assisi to any guru tells you that.
–– M. Feldenkrais[3]


He’d been three years self secluded in his darkened room. He’d painted the walls black. He’d worn an eye mask to further block out the light. In Leipzig, in early October 1848 Gustav Theodor Fechner left his blackened room. He found himself walking in his garden. Through his uncovered eyes he soaked in the beauty of the flowers around him. The plants, their souls “glowing,” offered kinship. His own soul glowing with the light of a shared within-ness, with “liveness,” accepted. It was morning, a preternaturally bright morning and it ended Fechner’s crisis of health.

The momentous morning was to last a lifetime. It formed the basis of his life’s work. He had “seen” seeing itself. He had seen the Nature of the world as being both infinite and particular. In it’s fullness it was, as Fechner designated it, “the Given.” To Fechner, the Given indicated the experience of being at once material and coequally a mind, psyche or consciousness. Two sides of the same coin. The dual aspects of observed material exteriority and observing interiority. Psycho-physical parallelism is one name for it and, Fechner maintained, it is the basic experience out of which all facticity emerges. The Given constitutes a common touchstone for all forms of scientific and philosophic enquiry as well as underpinning the arts.

Two sides. Fechner was a scientist. He rejected a singularly materialist approach. Nevertheless he embraced a conceptual and experimental rigor that led to the foundation of several domains of science, most notably Psycho-Physics. As Dr. Mises, a pseudonym, he wrote literary pieces, witty essays and parodies. Truth & Beauty.

Feldenkrais was also a scientist. He too rejected materialism. Face to face: Feldenkrais and Fechner. The Feldenkrais Method has a sort of “creation myth.” Born from a broken knee and a knee’s need to heal itself, the Feldenkrais Method emerged to fill that role. Moshe Feldenkrais was there to play his part. He brought to the task an expert’s working knowledge of many profound traditions of thought and practice. One lineage of theoretical and scientific practice Feldenkrais invoked was the Fechnerian tradition. Scientist, martial artist, story teller Feldenkrais ended up bringing something new and novel into the world. Less than 100 years separated Fechner’s invention of Psycho-Physics and Feldenkrais’s invention of his method. Fechner’s Given is Feldenkrais’s Elusive Obvious. If we learn a little more about Fechner we may know a lot more about Feldenkrais.

All thinkers in Fechner’s time had to confront the ideas of Charles Darwin. Was evolutionary theory valid and what were it’s mechanisms? Thinking through Darwin’s theory of evolution, Fechner formulated a “principle of the tendency to stability.” He wrote Ideas in the History of Organism Creation and Development (1873) the first known paper on what is now trendily called “self-organizing” systems.[4] Fechner outlined five principles for the ways inorganic matter and organic matter co-developed. He traced the various gradations or stages of dynamic stability and instability necessary to produce self-organizing systems. Fechner, researching aesthetics using his ideas of stability/instability, was led to postulate the principle of pleasure-unpleasure. Fechner’s pleasure principle figured into his attempts to found a psychology of wit and jokes. Fechner’s direct influence on Freud is transparent.

At the end of the Nineteenth century, Fechner seemed destined to be remembered only for formulating his “fundamental psychophysical law.” No scientist wanted to risk taking seriously his Philosophy of Nature. We are indebted to Sigmund Freud and William James for keeping Fechner’s work in the minds of many psychologists and scientists. Freud attended some of Fechner’s lectures and thoroughly studied his work. Freud incorporated into his psychoanalytic meta-psychology several basic concepts from Fechner’s Psycho-Physics and his Philosophy of Nature. Freud quotes Fechner in The Interpretation of Dreams, The Wit and the Unconscious, Beyond the Pleasure Principle and the Project.[5] Fechner’s concept of mental energy, his “topographical” concept of the mind (the partitioning of mind into unconscious, preconscious and conscious regions), his principles of pleasure-unpleasure, the ideas of constancy and of repetition all find their way with little modification into Freud’s grand scheme. On Freud’s debt to Fechner:

The principle of constancy is but one particular case of Fechner’s more general “principle of the tendency to stability.” Fechner distinguished three forms of stability: absolute stability (implying a permanent immobility of the parts of a whole), full stability (the parts of the whole are animated by movements so regular that each part of the whole returns to the same place at regular intervals), and “approximate stability” (a more or less imperfect tendency to return to the same place at regular intervals, as in the movements of the heart and other rhythmic psychological activities).[6]

Freud drew upon both Fechner’s systematization of psychodynamics and his experimental approach to the study of the unconscious. Freud built his death instinct on Fechner’s description of full stability and located repetition compulsion as an intermediate between approximate and absolute stability. In Fechner’s work the pleasure-unpleasure principle connects approach, the movement toward approximate stability, with pleasure. Retreat, a movement away from approximate stability, is connected with unpleasure. For Fechner, qualities of perception equated with the periodicities of a stable movement. Freud’s “economic function” described how mental forces are regulated through the pleasure-unpleasure principle and is “essentially identical” with Fechner’s concept. Freud utilized much from Fechner in his attempts to found a theoretical and clinical psychology of everyday life – Love, Death and Work. Hence, we understand Freud calling him “the great Fechner.”[7]

There is a significant difference between Freud’s and Fechner’s “pleasure principle.” In Freud’s theory of drives organisms have physiological needs that when unmet create anxiety and a negative state of tension. When a need is satisfied the drive tension is reduced giving pleasure as the organism returns to a state of homeostasis. The origin of the notion that it’s healthy to release “bottled up” feelings started with Freud. For Fechner pleasure was the concomitant result of the re-establishment of equilibrium (the more so if it can be established on a higher order). Freud: Pleasure = release of tension; Fechner: Pleasure = coming into dynamic equilibrium. We see in Fechner’s version a resonance with Feldenkrais’ rejection of “pent up” energies that must be released. Fechner would assent to the pleasure found in becoming “harmoniously balanced.” For Feldenkrais there’s additional joy to be had in knowing how to find balance.

William James devoted a good part of A Pluralistic Universe to Fechner’s metaphysical ideas. In James’s opinion: “Few professional philosophers have any vision”[8] in comparison to Fechner. Fechner was able to cast a wide philosophical net by grounding the feeling of both sensory and intellectual attending in “... bodily processes.”[9] James also liked Fechner’s nested hierarchically ordered approach to states of consciousness. For Fechner consciousness is attached or apportioned by degrees of cellular organization to any living organism from single celled organisms to human beings and beyond. And, “…that more inclusive forms of consciousness are in part constituted by the more limited forms.”[10]

The following is James’s reading of Fechner and it gives a good accounting of Fechner’s metaphysics, which have come down to us in one form as the Gaia Hypothesis:

Fechner likens our individual persons on the earth unto so many sense-organs of the earth’s soul. We add to its perceptive life so long as our own life lasts. It absorbs our perceptions, just as they occur, into its larger sphere of knowledge, and combines them with the other data there. When one of us dies, it is as if an eye of the world were closed, for all “perceptive” contributions from that particular quarter cease. But the memories and conceptual relations that have spun themselves round the perceptions of that person remain in the larger earth-life as distinct as ever, and form new relations and grow and develop throughout all the future, in the same way in which our own distinct objects of thought, once stored in memory, form new relations and develop throughout our whole finite life.[11]

James employs a couple of great metaphors to introduce and to give depth to Fechner’s ideas:

We rise upon the earth as wavelets rise upon the ocean.
We grow out of her soil as leaves grow from a tree.

William James, the brother of writer Henry James, leaves no doubt about his own ability to find and develop allusions. How to account for the individual and collective influences on us? How may we be influencing others?

The wavelets catch the sunbeams separately, the leaves stir when the branches do not move. They realize their own events apart, just as in our own consciousness, when anything becomes emphatic, the background fades from observation. Yet the event works back upon the background, as the wavelet works upon the waves, or as the leaf’s movements work upon the sap inside the branch. The whole sea and the whole tree are registers of what has happened, and are different for the wave’s and the leaf’s action having occurred.[13]

And how does a Fechner influence a Feldenkrais or a you or a me? Well, it’s in:

…being affected by the perceptive experiences of those living then, and affecting the living in their turn—altho [sic] they are so seldom recognized by living men to do so.[14]

And this individual sensorium made of parts and yet felt as my self, this organ of the universe that the universe uses to sense and communicate with itself as if an other, is what?

In ourselves, visual consciousness goes with our eyes, tactile consciousness with our skin. But although neither skin nor eye knows aught of the sensations of the other, they come together and figure in some sort of relation and combination in the more inclusive consciousness which each of us names his self.[15]

In the history of science there are winners and losers. Until recently Fechner was something of a loser. If he is remembered at all, it is as one of the first experimental psychologists and the founding father of theoretical psychophysics. He devoted his life—a long one (1801–1887)—to making a place within science for his anti-materialistic psychophysical world view—his “Day View.” With it he sought to counter the nihilistic entrenchment of scientific materialism—the “Night View”—into mid-nineteenth century science. To Fechner science was becoming increasingly dry, disconsolate and wrongheaded. The Day View, invested with what Fechner called “liveness,” shares common ground with early and mid-nineteenth century philosophies of Nature, physics, idealism and Romantic aesthetics. The Day View holds that the physical does not cause the mental nor that the mental causes the physical and neither do they cause each other.

Fechner… describes life and consciousness as having an independent, original nature that cannot be further reduced to physical phenomena…. Yet, at the same time, Fechner’s position is materialistic. He sees every change in the physical world as wholly explicable by the laws of nature, and he sees for every mental change some change in the physical world that precedes it. The intriguing thing about Fechner’s philosophy is just how he gets these two seemingly contrary tendencies of non-reducibility and materialism to harmonize.[16]

Backing up a bit. Toward the end of the 1830s Fechner had begun to shift his interest from physics to experimental psychology. He authored papers on the perception of complementary and subjective colors. In 1840, after authoring an article on subjective afterimages[17], Fechner suffered what’s now called by some a “nervous collapse” and others a “sublime hypochondrias” i.e., a creative illness. He had a painfully injured his eyes while gazing at the sun during his research. His injury, while not permanent, resulted in a temporary blindness and left him emotionally and physically drained. Giving up his professorship at Leipzig he went into his three year dark retreat. Secluded in penetrating darkness he moved from physics toward metaphysics.

In 1848 he returned to professional work and he completed Nanna (1848). In Nanna and in Zend-Avesta (1851) Fechner sketched out his Philosophy of Nature, a dual-aspect, monistic, pan-psychical mind/body view. In a famous metaphor Fechner likened the universe, which is at one and the same time both active consciousness and inert matter, to a curve that can be regarded from one point of view as convex and from another as concave. In line with his approach to mind/body, Fechner laid out a future program for Psycho-Physics—to demonstrate the unity of mind and body empirically by relating an increase or a decrease in bodily energy to a corresponding increase or decrease in mental intensity.

Fechner attempted to show that his dual-aspect theory of body and mind was a hypothesis that is testable and amenable to measurement. Fechner’s notion of measurement and the measurable is clearly presented in the Elemente der Psychophysik (1860/1966). Fechner’s approach was both deeply philosophical and rigorously mathematical. He sought to bring to light, the light of his Day View, life as lived materially and psychologically.[18] Fechner’s idea of how to measure mental events, his theory of comparative judgment, grows directly out of the thought of Carl Gauss (1821). Gauss had stated that “Errors,” arising from random causes and sources, “ … come from the imperfections of our senses and random external causes, as when shimmering air disturbs our fine vision.”[19] Gauss’s seminal work on probability theory and on understanding random errors is called the Gaussian Probability Distribution more commonly known as the Normal Distribution or Bell Curve.[20] It allows one to handle random errors in a mathematically rigorous way. Fechner applied Gauss’s application of mathematical analysis of statistics and errors to the measurement of a person’s comparative judgment, that is, their ability judge differences in sensation. Fechner thus had arrived at the physics of psycho-sensory perception.

Fechner succeed in his attempts to measure and give a mathematical analysis of such mental phenomena as the amount or “magnitude” of sensation, the “heaviness” of a lifted weight, etc. Through his attempts to measure the “beauty” of a painting he of necessity created the field of experimental aesthetics. His researches led to the introduction of new, original methods of descriptive statistics for which he deserves but did not receive credit.

Ernst Heinrich Weber the German anatomist and physiologist (1795–1878) was a direct influence on Fechner both as mentor and colleague. He first introduced the concept of the just noticeable difference (jnd), that is, the smallest difference perceivable between two similar stimuli. A jnd conveys the idea that a self-report of a sensation is a measure of a mental state. Weber determined that there was a threshold of stimulus that must be passed before an increase in the intensity of any stimulus could be detected as the sensation of difference; the amount of increase necessary to create sensation was the just noticeable difference. Interpreting the empirically derived jnd mathematically Fechner gave us his law which states that human perception follows a logarithmic rather than linear response. Common examples of logarithmic functions are the Richter Scale for earth quakes and decibels for audio volume. The famous constant of sensitivity, Δs/S = c, represents a differential equation whose solution yields a logarithmic function relating the magnitude of sensation to the magnitude of the physical stimulus. Distinguishing between inner psychophysics (the relation between sensation and nerve excitation) and outer psychophysics (the relation between sensation and physical stimulation), Fechner’s Law states that the intensity of a sensation increases as the log of the stimulus (S = k log R) to characterize outer psychophysical relations.[21]

The fact that human sensory discrimination is logarithmic is a profound insight.[22] It allows us to discriminate stimuli that range over many orders of magnitude. For example the threshold for human hearing is approximately 0 decibels (a ticking watch 20 feet away in a silent room) while a rock concert may be 120 decibels. This is a range of 1 trillion (10 to the 12th power) in acoustic power—a remarkable range for any sensor. The same logarithmic response holds for other senses. Fechner showed that the logarithmic sensory response could be derived from the mathematical description of the jnd.[23]

Fechner had arrived at a way of demonstrating a fundamental philosophical truth called the identity hypothesis, which holds that mind and body are not to be regarded as real but as different sides of one reality. Inseparably united and distinguished only by point of view, sensation appears from an internal subjective viewpoint as the mind and appears from an external objective viewpoint as the body. Fechner’s law was a testable way to make evident that dualism is not real. Gustav Theodor Fechner humbly named this law after Weber. Later theorists gave Fechner his due and renamed it after Fechner. His radical mathematical reformulation of Weber’s law became the first psychophysical law.

Despite Fechner’s intent to counter the Night View’s deadening materialism, his real impact and legacy was on scientific methodology. His competency in mathematics plus his systematic experimentation and not his “mysticism” became mainstream science. Methodological innovation and careful experimentation led Fechner to believe that the inseparable unity of sensory and mental experience could be quantified. His contemporaries lacked Fechner’s vision, eschewed the mental and succumbed to the Night View falling into what visionary poet William Blake called “Newton’s Slumber.”

When delving into the history of the Fechner-Weber Principle one is struck with the central role of the concept of a threshold. The threshold in the experimental and theoretical science of Psycho-Physics is where matter and mind meet, where a universe of quantity reappears as a universe of quality, consciousness and awareness. In its remarkable history the psychophysical threshold has been defined, denied, redefined. It’s a concept who’s worth is actively debated still today. It began with a simple set of questions, one of which is: How and by what measure does one define the point, line or zone where the physical becomes the psychical, where quantity becomes quality?

Uncertainty is a factor in deciding whether a faint stimuli has been detected or not. A sensory threshold (or limen) is the point of intensity at which one can just detect the presence of, or difference in, a stimulus. Due to this, a threshold is considered to be the theoretical point at which a stimulus, or change in a stimulus, is detected some proportion of the time. There are two kinds of thresholds: absolute and difference.[24] The concept of an absolute threshold is defined to be the lowest intensity, i.e. the smallest amount, at which a stimulus can be detected 50 percent of the time. The 50 percent figure is arrived at because any organism’s sensitivity to external stimuli tends to fluctuate somewhat from moment to moment and so several measurements of the threshold value of the stimulus need to be averaged to arrive at an accurate estimation of the absolute threshold. The difference threshold is defined as the magnitude of the smallest difference between two stimuli that can be detected 50 percent of the time and is named the just noticeable difference (jnd). The just noticeable difference stipulates that for the mind to distinguish among the many signals that define its state of existence, it must be capable of distinguishing those signals.[25]

Fechner asked another very simple yet powerful question: on what mental basis do we lay the claim for the capacity to distinguish the feel of weight? Start with data and a way to analyze that data. Ask a subject which of two objects weighs more. Fechner assumed in comparing weights that each object when lifted produced sensations of heaviness that were mentally added together. Assume then that the average of the two heavinesses becomes a standard or internal mental referent against which an individual heaviness is judged. Any judgment as to which object is heavier must be based upon a comparison to the standard or referent. The heavier of the two objects was judged through comparison to the internal referent to be heavier than the average of the two. The lighter was judged by comparison to the referent to be less than the average. It is vitally important to realize that the difference lies not in the objects but in the comparison.

If the actual weight difference between two objects is below the threshold of sensory discrimination then the judgment of the weight of the measured object would be random and the error would be 50%. For slightly larger differences the judgment error would be slightly reduced. Fechner defined the jnd to be the amount that results in an error half way between certainty and random chance, that is the amount that produces an error 25% of the time. Fechner reasoned that the jnd was a unit of “mental” measurement and as such a psychological constant in the way a centimeter is a constant unit of length. Fechner thought that the jnd was a constant fraction of the stimulus regardless of the size of the stimulus. This generalization of the idea of constant sensitivity is named Fechner’s Conjecture.[26]

Fechner’s Conjecture permitted Fechner to use in his comparison experiments any multiple of any two weights. Weber had determined empirically that given a pair of comparison weights any multiple of these weights should produce judgments equally in error: Lifting 40 lbs. requires the addition of 1 lb. for a jnd; 20 lbs. requires only ½ lb; 10 lbs. requires ¼ lb and so on. The methodology was called the Method of Multiplying Stimuli and with it Fechner demonstrated both its usefulness and its support for the principle of constant sensitivity. It is this relationship that Fechner used to mathematically show that the relation of stimulus to sensory response is logarithmic.

Fechner’s Legacy

In tracing Fechner’s legacy in Psycho-Physics there are some names and advances that deserve mention. First, they took Fechner seriously and secondly, they contributed to Fechner’s relevance today. Fechner’s heirs have expanded the view and scope of Psycho-Physics in ways that bear upon the Feldenkraisian tradition. If we view the progress made on Fechner’s original insights by subsequent thinkers we can see how the questions they asked and the research they conducted refined the notion of what is or isn’t measurable and what is the role of the subject’s responsiveness in sensing and judging. Even a cursory examination of some of the research should prove inspirational to Feldenkrais practitioners.

Years of experiments by Fechner demonstrated his generalization of Weber to be accurate. In his Method of Right and Wrong, in cases where responses could not be determined to be heavier or lighter because of “an interval of uncertainty,” Fechner treated the response as both right and wrong. Later researchers would observe:

By varying the amount of difference and making it in some cases so large that it was usually perceived correctly, we have combined the method of right and wrong cases with the method of the just noticeable difference. This shows clearly that the method of just noticeable difference in its scientific form is simply a case of the method of right and wrong cases.[27]

In a sterling study on the perception of minimal differences, it was noted:

So far as the threshold implies that “sub-liminal” differences provoke a judgment different in quality from those due to larger differences, it is a misleading concept, and unsupported by fact.[28]

The first critical assessment of Fechner’s work backed up by new experimental data was written by Charles Sanders Peirce (1839–1914) scientist, mathematician, philosopher, founder of semiotics and of American pragmatism. Peirce contributed three things central to subsequent Psycho-Physics research: 1) a better mathematical tool; 2) a recognition of sub-threshold awareness; and 3) a new line of research, the application of mathematics to not just sensory differentiation but also to reasoning under uncertainty.

Years before the research cited above, Peirce asked, “Can a difference which does not affect our consciousness affect our judgment? Do differences that are below consciousness act on us or are they as if to be considered as no difference?” Peirce followed a line of reasoning different from Fechner:

… the errors of our judgments in comparing our sensations seem sufficiently accounted for by the slow and doubtless complicated process by which the impression is conveyed from the periphery to the brain; for this must be liable to more or less accidental derangement at every step of its progress.[29]

But what methodology best applies? According to Peirce, the Method of Least Squares.[30] Peirce:

Accordingly we find that the frequencies of errors of different magnitudes follow the probability curve, which is the law of an effect brought about by the sum of an infinite number of infinitesimal causes. This theory, however, does not admit of an Unterschiedsschwelle [difference limen or threshold—DL]. On the contrary, it leads to the method of least squares, according to which the multiplication of observations will indefinitely reduce the error of their mean, so that if, of two excitations, one were ever so little the more intense, in the long run it would be judged to be the more intense the majority of times…[31]

But what about the just noticeable difference? For Peirce the math should not only conform to experience but be predictive as well:

If there be a least perceptible difference, then when two excitations differing by less than this are presented to us, and we are asked to judge which is the greater, we ought to answer wrong as often as right in the long run. Whereas, if the theory of least squares is correct, we not only ought to answer right oftener than wrong, but we ought to do so in a predictable ratio of cases.[32]

In his experiments Peirce used an external fixed weight for comparison, which differed from Fechner who had compared two weights, assumed their mentally summing and fixing the average of the two to be the internal referent. And Peirce’s research showed that under uncertain conditions, when differences seemed to have disappeared or alternately to have not appeared, subjects did indeed choose correctly within a band or range of differences close to the jnd but definitely below it. What Peirce is saying is that we can and do as human beings make accurate judgments that are based upon differences that are not conscious, that are below threshold. And, not only do we do that to a degree of accuracy greater than chance but that a methodology predicated upon the Method of Least Squares says it must be the case. Differences that make a difference need not be conscious.

Peirce needed a way to scientifically shore up his philosophy of Pragmatism. It was a central tenet in Peirce’s Pragmatic philosophy that playing hunches and our predilection for guessing were evolutionarily advantageous. Hunches, if not immediately accurate, are most often wrong in the right direction. His formalization of the notion of guessing, he called abduction, contrasting it to induction and deduction. Peirce’s mathematical advance on Fechner’s work was acknowledged by subsequent researchers, but not his conclusion. It was held that rather than proving Fechner wrong Peirce rather drew out an important implication of Fechner’s work: the jnd could be noticed and acted upon unconsciously. The implication of unconscious perception certainly did not escape Freud.

Neither did it escape Feldenkrais. Both Peirce and Feldenkrais held that in daily life one should follow one’s “gut” or “instincts,” i.e., habits. Both again stated that while we can improve our theories in carefully controlled experiments and improve our lives through aesthetic refinement, when push comes to shove, go with what’s worked. Crucial to Feldenkrais’s worldview is the idea that we shouldn’t live our lives according to “ideals” or theories, that we should be wary of doing things that are “good” for us and that the use of conscious will in habit change is detrimental to our well being. As always, it’s greater awareness rather than more consciousness that will prove to be the more beneficial to our lives.

Peirce also provided a new basis for research by adding another dimension to Psycho-Physical research: response confidence. While Fechner had made note of a perceived “interval of uncertainty” in the test subject’s response, Peirce demanded it’s empirical measure:

… speak of the chance of an event absolutely, meaning by that the chance of the combination of all arguments in reference to it which exist for us in the given state of our knowledge. Taken in this sense it is incontestable that the chance of an event has an intimate connection with the degree of our belief in it. Belief is certainly something more than a mere feeling; yet there is a feeling of believing, and this feeling does and ought to vary with the chance of the thing believed, as deduced from all the arguments.[33] [emphasis added, DL]

Belief for Peirce was a feeling we are willing and able to act upon. The “weight” of that feeling has as its poles Absolute Certainty and Infinite Chance neither of which are knowable by mere mortals. Somewhere there’s a zone where as chance is diminished believing comes to the fore. Conversely when chance increases or rather when any action or choice has an even chance of success or failure, belief, a particular belief, will weaken and vanish. If a belief cannot hold as it’s chances of success diminish then a contrary belief should spring up. Peirce extended Fechner’s argumentation concerning sensory discrimination to the domain of belief:

It is that our belief ought to be proportioned to the weight of evidence… that two arguments which are entirely independent, neither weakening nor strengthening each other, ought, when they concur, to produce a belief equal to the sum of the intensities of belief which either would produce separately.[34]

Take the chances of independent but concurrent arguments, multiply the chances to get the chance of their combination and you’ll have the quantities expressing the intensities of belief such that when they are added and their choices multiplied so that together they’ll produce a quantity corresponding to their combined chance. Peirce:

Now, the logarithm is the only quantity which fulfills this condition. There is a general law of sensibility, call Fechner’s psycho-physical law. It is that the intensity of any sensation is proportional to the logarithm of the external force which produces it. It is entirely in harmony with this law that the feeling of belief should be as the logarithm of the chance. This latter being the expression of the state of fact which produces the belief.[35] [Emphasis added, DL]

Take the sum of all the feelings [i.e., log-odds] of belief which would be produced separately by all the arguments pro and subtract from that the similar sum for arguments con, and the remainder is the feeling of belief we ought to have on the whole. This is a procedure which men often resort to, under the name of balancing reasons.[36]

Peirce does something remarkable here. He was the first to formally apply mathematics to decision making in the face of uncertainty. Knowing that he is not measuring physical quantities Peirce instead proposes a way to measure the “weights” of our competing beliefs. He asked how confident on a scale of 1 to 4 was the subject’s choice of heavier or lighter. So, first he measured the subject’s sensory acuity and then he measured the subject’s confidence in their sensory judgments. He showed that they both operationally follow Fechner’s logarithmic formula. In our Feldenkrais pedagogy we have the means for making and evaluating sensory-motoric distinctions. What we have not developed are the means for relating and linking feelings of confidence to competence. Both are learnable skills but they do not deal with the same content. The ideas worked out in Fechnerian psychophysics are rich in practical implication and we in the Feldenkrais community are much the poorer for not employing them.

Other significant contributions to Fechner’s legacy were made. Researching the particulars of psychophysical measurement evolved in the first phase from the study of sensation to “subjective factors.” In the second phase it was largely “subjective factors.” Finally, in the third phase the movement was from subjective factors toward unifying principles and yet more sophisticated mathematical analyses. Studied in the first phase were: force and duration of bodily movement; intensity of sensation and response time; ways to test and measure behavior without “self reports of mental states.” And, new concepts were introduced: a distinction between response time versus response frequency; units of time (as duration) of perception; a measurable size of an “interval of uncertainty”; that inward or “subjective” factors be thought of as a condition of the organism itself in modifying its reaction; that the subject’s attitude affects sensitivity; that “heaviness” must be learned. Approaches to measure the previously unmeasurable were developed: a Law of Comparative Judgment to measure affective values, that is, the feelings that arise in aesthetic appreciation; a serviceable evaluation of the “seriousness” of a crime; and, testing how one chooses to judge things that matter, e.g., “the beauty of flowers, the appeal of paintings, the aroma of culinary delights, or the bouquet of vintage wines.”[37]

The next phase of experimenters and theorists laid the groundwork for a fundamental reordering of Fechner’s work. Heretofore, two-choice more or less test scenarios were the norm. The question arose as to how to test and define sameness. In judging that some sound different, that is, louder or softer fewer errors are made than when determining if it’s the same intensity. On the other hand, if the errors in judgment regarding sameness are greater, so too prove the benefits of training to reduce those errors. The question arose: Does the time taken to make a choice vary consistently with the amount of difference in the affective values (the term used to cover aesthetic judgments) of alternative stimulus-objects? Of course the answer was “yes” and interestingly (and not surprisingly) experiments showed that for objects we really like or really don’t like the response times to make a choice were shorter. The objects attached to neither a strong like or dislike garnered the longest response times. The point here is that although intending to test aesthetics proper it was becoming apparent to researchers that there is a relationship between response time and the subject’s willingness to respond. Whether measuring response time and confidence or measuring speed versus accuracy, researchers saw that response time increases while confidence decreases as we come close to the threshold of discriminability. Response time and probability came to be linked to a single judgment mechanism and it was recognized that the attitude of the subject strongly affects sensitivity and probability.

Now it gets even more interesting, as Clyde Coombs proposed the Theory of Ideals. Imagine each subject has a continuum of psychological values created by stimuli. Imagine that one of those values is an Ideal for the subject (a shade of gray, a tone, a pressure, etc.) When the subject is asked to order them, to place or order choices of stimuli on an absolute scale, that is, place a shade, tone or pressure in its proper place in continuum, it is found that choices in the neighborhood of the Ideal will show the subject’s biases. Biasing creates a disordering or confusion in the area of the Ideal and therefore some inconsistency. The inconsistency will bias response time as well as accuracy. The inconsistency is a consequence of the placement of an Ideal and not a consequence of a noncompliant or insensitive subject. Subjects weigh their comparisons of psychological values of stimuli against Ideals. Further determinants of response time bias include the forcing of choices by requiring speedier or more accurate choices or tweaking motivation through rewards and/or punishments.

As the field of Psycho-Physics progressed contributions and extensions to Fechner’s work grew and supposed contradictions began to appear. In the early 1990s there appeared a set of mathematical tools with the power both to clarify the object of psychophysical study as well as integrate all its apparent contradictions. The problem was posed like this: How does one make a choice between judging a work of art by Michelangelo as better or more beautiful or more provocative than one by Leonardo DaVinci? And, how does that judgment mechanism compare to a judgment mechanism where we decide one weight to be heavier or lighter? We all routinely make judgments of both simple and complicated stimuli. We can build upon Peirce’s idea of possessing necessarily a single mechanism for both types of judgment. It’s only the input to the judgment process that changes. A judgment about the luminance of a Da Vinci masterpiece differs from a judgment about the brightness of a halogen light against differing backgrounds only in the selection of data from the stimuli, not in the mechanism for judgment. What approach reconciles the two mechanisms?

It must be noted that the stimuli in question are neither the paintings nor lights themselves. Rather, it is the physicality of the paintings or lights as “seen” by a mind making the comparison that is in question. It was Stephen W. Link who found a way using Poisson distributions[38] to unify the various empirical and mathematical approaches to psychophysics. According to Link’s theory put forth in his Wave Theory of Difference and Similarity:

The process of seeing involves the neural transduction of the proximal stimulus into a central, unobservable, psychological stimulus. Wave Theory posits that within the body all stimuli are electrical signals—the physical manifestation of messages transmitted through the body. Messages travel through the body, but over time. Therefore, signals are components of a complex time amplitude electrical waveform. Many such signals may be combined and transmitted within a single waveform. Thus, many signals may be present at the same time. From this potentially chaotic ensemble of signals those signals of interest can be filtered from the ensemble any time, at will. That is, the mechanism of attention can select components of the waveform, qua stimulus, at any time.

At the level of probability distributions this view is indistinguishable from the 19th-century view proposed by Fechner. However, much information exists in a sequence of amplitudes that does not exist in the probability distribution itself. The existence of this added information permits the analysis of mental mechanisms through the application of stochastic (probabilistic) processes.[39]

And in a review, Link’s work is summarized by stating:

… On each trial, the observer samples the stimulus continuously over time and the result is the envelope of a time-amplitude waveform. At any point during the sampling process the value sampled from the stimulus wave is subtracted from a value sampled from a referent wave, and the result is a comparative wave. The differences between the sampled wave and the referent wave cumulate over time until the sum exceeds the observer’s threshold. The response to the stimulus starts as a quantized action of sensory receptor modeled by a Poisson process, which allows for the prediction of sensation magnitude functions. This theory… focuses on stimulus energy...[40]

In Link’s theory, all judgments spring from a determination of more or less or from a determination of same or different. The two fundamental mechanisms become evident from within Wave Theory and resolve conflicts that had arisen in the work of previous researchers. Link’s work is pertinent to understanding sensory discrimination and its relation to stimuli but also to:

…the broader class of stimuli of general interest to all psychologists, stimuli that please, disturb and sometimes soothe the human spirit.

Feeling differs from sensation… The view put forth in Wave Theory is that sensation is the awareness of a stimulus but feeling is the measure of awareness. The feeling created by a stimulus is the perceived magnitude of the stimulus as seen by the subject who is aware of it.[41] [emphasis added, DL]

Wave Theory provides a unique approach for measuring the influence on discrimination of “subjective factors.” All judgments end in a single two-choice stimulus-response path termination: either more/less or same/different. The range of stimuli can include paintings, social issues, ideas or the more purely sensory stimuli of early experimental psychology. And, as in any good theory, our knowledge of our human universe may be extended in surprising and profound ways. Link:

A subject’s mental analysis of these stimuli depends upon the nature of the question put to the subject. Certain complicated judgments, not yet investigated, may require the accumulation of wave values drawn from several mechanisms. Some judgments may require parallel or even competing mental processes. The combination of primitive mental processes provides an avenue for developing new models of thought processes and feelings… By creating new mental processes Wave Theory brings to human understanding thoughts we cannot think and emotions we cannot feel.

The two variables under the direct control of the subject prove to be controlling features of observable behavior. Response bias proves to be a ubiquitous property of psychophysical experiments and is a cause for the often observed Constant Error. The resistance to respond is the second factor under direct subjective control. Resistance to respond influences both response probability and response time.[42]

The amount of sensation depends upon discriminability and the subject’s resistance to respond. This measure of sensation is consistent with previous meanings but is enriched by the expression of subjective control over the amount of sensation. Links formula written prosaically is: Sensation = Discriminability x Resistance to Respond (and hence Resistance = Sensation / Discriminability or Discriminability = Sensation / Resistance). The inclusion of a subjective component of sensation changes dramatically the interpretation of many experimental results. We can never again discount subjective factors as has been done in the Behaviorist school. Fechner is vindicated.

Link reexamines the notion of “sub-threshold” or subliminal sensations that paradoxically emerge from unfelt stimuli. Technically, what differentiates perceived sensations and the stimuli generating those perceived sensations from unperceived stimuli is that when compared against the absolute-threshold stimulus unperceived stimuli are perceived to be greater than the absolute threshold stimulus on less than 50% of the trials. In other words, the stimuli affect us but are not consciously sensed.

The Wave Discrimination Theory of discriminating the presence of a stimulus from no stimulus at all requires the subject to compare the experimenter’s stimulus against an internal referent. If anything is absolute, it is this internal base against which a sample of the sensory surround is compared. Thus, a comparison stimulus which on the average is smaller than the absolute-threshold stimulus tends to produce negative values.[43] [Emphasis added, DL]

Negative values is another way of saying not conscious. But, they are still capable of having an effect. Saying “If anything is absolute, it is this internal base…” is saying that we can’t get away from making comparisons relative to an internal base consciously, sub-consciously or unconsciously. We can, however, design situations in which we turn that process of comparison toward the mutual benefit of ourselves and others.


For Feldenkrais practitioners it’s a commonly held notion that when Moshe Feldenkrais invoked the Fechner-Weber Law it was as an encouragement to reduce effort while learning. In part yes, but actually Feldenkrais was calling forth a forgotten lineage: those researchers who brought the psyche, “liveness” and awareness into the realm of scientific consideration. Fechner’s lineage is amply covered in Nature from Within, Michael Heidelberger’s very thorough biography of Fechner, and Link’s book Wave Theory of Similarity and Difference with its fine overview of Fechner’s legacy. Reviewing the history of Psycho-Physics it’s plain that science and mathematics have an essential role to play in understanding our selves. Essential, that is, when Fechner’s Day View is our starting point. For Fechner, for his followers, and for Feldenkrais scientific rigor and mathematical analysis help plumb the depths of human experience, help ask new questions and rethink old answers. For a Fechner or a Feldenkrais the goal is not to stay with analysis, theory and reduction. The goal is finding a door leading to the Elusive Obvious and to bringing forth the Given.

The pleasure of learning, which as Aristotle has taught us is the greatest of all pleasures, can be recast in the light of Fechner. Given that for Fechner pleasure arises when we regain balance psychophysically, then regaining balance is one way of describing learning. Our habits, whether life affirming or life denying, can be viewed in the light of a dynamical systems perspective. Habits, thought of as dynamically stable states are relatively imperturbable. Given the right impetus they can be perturbed, made unstable, giving rise to another dynamically stable state that is more inclusive, more rooted in and more attuned to the flow of lived time. While learning with reduced effort is its own reward the full import of Fechner to us is in integrating our mechanisms of judgment with more strata of our lived experience. In a Feldenkrais lesson the different strata of experience are reconfigured and they are revalued. Habit’s most intimate dynamical machinations are accessible and amenable to our tinkerings.

We need to ask the question “So what?” What are the methodological and theoretical implications of Fechner’s work for Feldenkrais practitioners? First of all, we now see that Moshe Feldenkrais could be included in the Fechnerian tradition. Fundamentally like Fechner he eschews mind/body dualism. Feldenkrais assumes, based upon his own experience and the experience of thousands of students, that we can learn to measure and to judge for ourselves qualities as well as magnitudes of experience. In one sense each and every Awareness Through Movement lesson is an experiment into the means to make judgments as well as an examination of the apparatus of judgment. In another sense each lesson is a lesson in the art of living. Both senses of a lesson are congruent with the work of Fechner.

As Link has pointed out, Fechner’s work can be generalized to rest on two fundamental, primitive mechanisms of judgment: 1) sameness or difference or 2) more or less. That means, whatever criteria we use—lighter/heavier, higher/lower, longer/shorter, cooler/warmer, dry/moist, darker/lighter, rougher/smoother, now/then, etc.—they can be generalized to the mechanisms of either more/less or same/different. In asking our students to sense differences or similarities or to discriminate a more or a less we can consider ourselves in the Fechnerian tradition. Nuances in determining a difference or a sameness, or in deciding a more or a less can be confusing but with training both competence and confidence can be greatly improved.

When we say “notice differences…,” we situate the location of possible differences in time (then versus now) or space (left versus right, front versus back and so on). We may give differences an array of possible criteria. We say, notice if your impressions have changed. But what is a difference? Where does it reside? What is the experience of no difference? What is the value of uncertainty, that is, of not knowing? What happens if we just guess? Fechner’s tradition can and does address both the form and substance of such questions. It also provides insight into how it is we make or don’t make comparisons. It is in the notion of an internal referent that Fechner has the most to offer. Link: “If anything is absolute, it is this internal base against which a sample of the sensory surround is compared.”[44] When we really look into our experience of ourselves and our world it is how we relate our internal base to the ongoing process of life as is it being lived that determines the quality and depth of our lives. We can operationally access that base through two separate but related concepts: self image and primary image.

Feldenkrais’s confusing notions of a changeable, mutable self image and its relation to his idea of a vital and constant primary image can be directly related to Link’s internal base. In our pedagogy we address operationally on a process level all of Link’s terms—sensation, discriminability and responsiveness. What is not clear in the general understanding of Feldenkrais practitioners is how judgments in the realms of sensation, thinking, emoting and moving are attuned to one’s individual experience via reference to the internal base. As we apply various criteria for judgment we come into contact with our base of comparison, our self image. We observe that it is mutable and reflects our moods, intentions plus our personal history. Through the learning process as conceived by Feldenkrais we begin to find another base for reference, the primary image. It is a dynamically objective continuously stable backdrop for the experience of awareness. Feldenkrais has a sophisticated conceptual yet very concrete understanding of awareness. In the Feldenkraisian tradition it is awareness and not consciousness that harmoniously attunes us via orientation, enactment and timing to the three worlds of inner, outer and the in-between. Fechner’s legacy provides us with new tools—new ways to understand the relationship of sensation to discriminability and responsiveness—which allow us to even more appreciate our own Feldenkraisian approach.

As we are never just sensing or just moving or just thinking or just emoting we are in need of a way of relating them all that brings us to a higher grade of Being. That way is called a practice. It is how and what we practice that determines who we are. In certain moments the machinery of our habits does not hinder an authentic impression and expression of who we are. In those moments we are compelled to find a way out of the nightmare of our ignorance and to find a way to live more authentically.

In my experience the real reason underlying peoples’ complaints of their state of strain, anxiety, etc., is, in every case, ignorance. Not personal ignorance, which can be remedied by asking help from those who know better, but a much worse type. I mean the fundamental ignorance which creeps into science itself; abstractions that are generalized and temporarily exaggerated do incalculable harm. We know, in fact, very little about what life is, what is important and what is not.[45]

It cannot be emphasized enough that Feldenkrais points to a way of Being beyond whatever desirable and positive changes people nearly universally experience from lessons—gracefulness, ease of movement, alleviation of aches and pains and so on. The changes will be ephemeral unless they are intimately connected to an experience of the Given, to the Elusive Obvious. Both Gustav Fechner and Moshe Feldenkrais saw the same light, the light that dispels the nihilism and cynicism associated with Western culture for the last 150 years.


1. A. N. Whitehead, Nature and Life Greenwood Press 1970 Pg 30
2. M. Heidegger, (translators) Gregory Fried, and Richard Polt An Introduction to Metaphysics, Yale University Press, 2000 p37
3. Feldenkrais, Moshe. San Francisco 7/24/75.
4. Prigogine, Ilya, and Glandsdorf, P. L’écart à l’équilibre interprété comme une source d’ordre structure dissipatives. Bulletin de la classe des sciences, 59 (1973): 672-702.
5. Ellenberger, Henri F. The Discovery of the Unconscious: The History and Evolution of Dynamic Psychiatry (Basic Books, 1970), 514.
6. Ibid., 479.
7. Binswanger, Ludwig. Being-in-the-World: Selected Papers of Ludwig Binswanger, trans. Jacob Needleman (New York: Basic Books, 1963), 176.
8. James, William. The Writings of William James: A Comprehensive Edition. Edited, with an introduction by John J. McDermott, including Annotated Bibliography of The Writings of William James (Modern Library G 96). (The Modern Library, 1909/1968), 165.
9. Myers, Gerald E. William James: His Life and Thought (Yale University Press, 2001), 193. “The central feeling of attending—intellectual or sensory—is essentially connected with bodily processes.”
10. James, Writings, 155.
11. Ibid., 170.
12. Ibid., 171.
13. Ibid., 171.
14. Ibid., 172.
15. Ibid., 149.
16. Heidelberger, Michael. Nature From Within: Gustav Theodor Fechner And His Psychophysical Worldview (University of Pittsburgh Press, 2004), 73.
17. Roeckelein, Jon. Imagery in Psychology: A Reference Guide (Praeger, 2004), 25-6.
18. James, Writings, 175. “Day View: For him [Fechner] the abstract lived in the concrete, and the hidden motive of all he did was to bring what he called the daylight view of the world into ever greater evidence, that daylight view being this, that the whole universe in its different spans and wave-lengths, exclusions and envelopments, is everywhere alive and conscious.”
19. Fechner, Gustav. Elements of Psychophysics (Holt Rinehart & Winston, 1966), 87.
20. Gauss, Carl.
21. Fechner’s Law states that the intensity of a sensation increases as the log of the stimulus: S = k ln(S B /S 0) where S is the sensation, S B is the stimulus and So is the absolute threshold stimulus. This law arises from directly integrating the differential form of the equation for the famous constant of sensitivity Δs/S = c.
22.Logarithms have a profound and pervasive application in the real world. Richter Scale a level 2 earthquake is a hundred times more powerful than a level 1. A level 3 is a thousand times more powerful (103) and a level 4 is ten thousand times more powerful, and so on.
23. Link, Stephen. The Wave Theory of Difference and Similarity (Lawrence Erlbaum, 1992), 203-204.
24. Galanter, “Direct Measurement of Utility and Subjective Probability” American Journal of Psychology 75 (1962): 208-220

–––––––Poetical Absolute Thresholds
Vision – Candle flame 30 miles away on a dark, clear night
Hearing – Ticking watch 20 feet away in a silent room
Taste – Teaspoon of sugar in 2 gallons of water
Smell – Drop of perfume in 3 rooms
Touch – Fly’s wing falling on your cheek from height of 3 inches

25. Link, Wave Theory, 5.
26. Ibid., 11-17.
27. Fullerton and Cattell, cited in Link, Stephen. The Wave Theory of Difference and Similarity (Lawrence Erlbaum, 1992), 31.
28. Brown, cited in Link, Stephen. The Wave Theory of Difference and Similarity (Lawrence Erlbaum, 1992), 19.
29. Peirce, Charles Sanders & Jastrow, Joseph. “On Small Differences in Sensation” (1885), in Memoirs of the National Academy of Sciences 3: 73-83.
30.Wikipedia: The Method of Least Squares: The Method of Least Squares is used to approximately solve overdetermined systems, i.e. systems of equations in which there are more equations than unknowns. Least squares is often applied in statistical contexts, particularly regression analysis. Least squares can be interpreted as a method of fitting data. The best fit, between modeled and observed data, in the least-squares sense is that instance of the model for which the sum of squared residuals has its least value, a residual being the difference between an observed value and the value given by the model. The method was first described by Carl Friedrich Gauss around 1794. Least squares corresponds to the maximum likelihood criterion if the experimental errors have a normal distribution and can also be derived as a method of moments estimator. Regression analysis is available in most statistical software packages.
31. Pierce, Jastrow, “On Small Differences in Sensation”, 73-83.
32. Ibid.
33. Ibid.
34. Ibid.
35. Ibid.
36. Ibid.
37. Link, Wave Theory, 67.
38. Wikipedia: Poisson distribution: In probability theory and statistics, the Poisson distribution (pronounced [pwasõ]) is a discrete probability distribution that expresses the probability of a number of events occurring in a fixed period of time if these events occur with a known average rate and independently of the time since the last event. The Poisson distribution can also be used for the number of events in other specified intervals such as distance, area or volume.
39. Link, Wave Theory,141-2.
40. Gescheider, George A. Psychophysics: The Fundamentals (Lawrence Erlbaum Associates, 1997), 369.
41. Link, Wave Theory, 240.
42. Ibid., 317.
43. Ibid., 207.
44. Ibid.
45. Feldenkrais, M. Body & Mature Behavior (International University Press, 1996), 12-13.


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Link, Stephen. The Wave Theory of Difference and Similarity. Lawrence Erlbaum, 1992.
Heidelberger, Michael. Nature From Within: Gustav Theodor Fechner And His Psychophysical Worldview. University of Pittsburgh Press, 2004.
Pribram, Karl H., and Gill, Merton M. Freud’s ‘Project’ Re-assessed: Preface to Contemporary Cognitive Theory and Neuropsychology. Basic Books, 1976.
Fechner, Gustav. Elements Of Psychophysics. Holt Rinehart & Winston, 1966.
James, William. The Writings of William James, a Comprehensive
: Edited, with an introduction by John J. McDermott, including Annotated Bibliography of The Writings of William James (Modern Library G 96). The Modern Library, 1968.
Ellenberger, Henri. The Discovery Of The Unconscious: The History And Evolution Of Dynamic Psychiatry. Basic Books, 1981.
Roeckelein, Jon. Imagery in Psychology: A Reference Guide. Praeger, 2004.
Einige ideen zur schöpfungsund entwicklungsgeschichte der organismen. Leipzig: Bretkopf und Härtel. Ideas in the History of Organism Creation and Development (1873)