Quantum Drummer

Research Practicum

Abstract

       In the time period between 1913 and 1930, Niels Bohr and his team of scientists at the Copenhagen Institute developed the theories of quantum physics, one of the most complete and complicated set of knowledge regarding the way the universe behaves. This work is known as the Copenhagen Interpretation of quantum theory. In order to develop this work, they were required to break the dogma and paradigms of classical physics, and enter in a strong debate with Einstein and other leading scientists of the time. Bohr’s atomic theory from 1913 and his views on complementarity from 1927 conform a radical separation from the previous Newtonian paradigm.

       Bohr’s quantum theory and Einstein’s theories of relativity generated one of the major paradigm shifts in the history of human knowledge. These theories changed drastically the way that objective reality is perceived, moved around the place of humans in the universe, and made the scientific community enter into a long philosophical discussion.  One of the main concepts introduced by Bohr as part of the Copenhagen Interpretation of Quantum Mechanics is the concept of complementarity, which appears to be a concept that had been proposed earlier by William James. Also, in other parts of the evolution of modern physics, there is evidence of the influence of psychology, such as the case of the works of Percy Williams Bridgman, Harvard physicist and philosopher with a strong pragmatist background that seems to have been influenced by William James and C. S. Peirce while Bridgman was a student at Harvard in the early 1900’s.

       The understanding of where new ideas come from in any scientific field is important, and given the impact on human knowledge brought about by the changes introduced by modern physics, it is especially important to understand the root and genesis of these ideas. Also, finding evidence of the influence of psychology on the development of the main theories in physics, even if this has been informal and indirect, will provide an indication that science and humanism are not completely separated, and need each other to develop new knowledge.

Purpose

      The purpose of this historical research focuses in understanding how psychology influenced modern physics at the philosophical level, particularly by analyzing the philosophy behind the works of P. W. Bridgman, as a possible initial connection to the works of Bohr. Evidence of this influence might provide information of how the humanistic and scientific fields interact with each other, and need each other to grow their knowledge, demonstrating that neither field works isolated from each other.

Background

       Historians of science have tried to look for Bohr’s sources of inspiration, even outside of the domain of pure science, and the most accepted belief is that Bohr was able to achieve this task because he had a special philosophical background, very different from his contemporary peers (Favrholdt, 1992, p. 6).

      There is some evidence that seems to point out that Bohr received influence from the works of William James, particularly in regards to the development of complementarity. Holton (1973) indicates that among German scientists Bohr used to mention James but only a few other philosophers, and his 1929 work The Quantum of Action and Description of Nature aligns perfectly to William James’ chapter on the ‘Stream of Thought’ in James’ book, The Principle of Psychology (p. 122). The physicist Leon Rosenfeld, close colleague of Bohr’s, points out that Bohr became interested and excited about James’ work until around 1932, many years after the completion of his theories. Rosenfeld also says that Bohr himself told him one time that “you must not forget that I was quite alone in working out these ideas, and had no help from anybody.” (Holton, 1973, p. 122).

       On an interview with Bohr, held on November 17, 1962 by T.S. Kuhn, A. Petersen and E. Rudinger one day before his death, Kuhn asked him whether he actually read some of the works of various philosophers. Bohr recollects that with intervention of his friend Rubin, who was a psychologist, he read the work of William James, and specifically mentions “The Stream of Thought” chapter from James’s book. From this interview, the exact time when Bohr read James’ work is not clear, and this interview only adds to the debate between the believers of James’ influence on Bohr and the believers of Bohr’s independent work. (Holton, 1970, p. 1035).

       One possible way to connect James to Bohr is by looking for physicists that could have been in contact with James between 1890 and 1910, the time in which James developed most of his important philosophical work, and later could have participated and influenced Bohr in Copenhagen. The possibility of a transfer of ideas and knowledge could have occurred at Harvard, given that at the specified period of time Harvard was a very small community and could have been the perfect environment for this type activity among scholars from the fields of psychology and physics. There is a possible connection between physicists at Harvard and the works of James through the American physicist J. C. Slater who worked in Bohr’s team in Copenhagen, and in 1924 co-authored with Bohr and Kramers the famous “BKS” paper. (Beller, 1999, p. 23). Slater did graduate studies in Physics at Harvard, and was an assistant to Professor Percy Williams Bridgman (Kuhn, T. & Van Vleck, J., 1963, p. 12). Bridgman arrived to study physics at Harvard in 1900 and later became a distinguished physicist known for his interest in philosophy and pragmatism (Kremble & Birch, 1970, p. 24). Exactly how much, if any, contact Bridgman had with James and how much of the latter’s philosophy could have been transferred to Slater and eventually to Bohr is unknown, but this might be worth analyzing as a potential source of connection between James and Bohr.

Percy Williams Bridgman

        Percy Williams Bridgman started his studies of physics, mathematics and chemistry at Harvard College in 1900, and graduated summa cum laude in 1904. He stayed at Harvard through all his life, working in the department of physics first as a graduate student, obtaining his Ph.D. degree in 1908, becoming first a Research Fellow, and obtaining progressive academic positions until his retirement and appointment as professor emeritus in 1954. (Kremble & Birch, 1970, p. 26). His main area of work was in the field of high pressures, and in 1946 he was awarded the Nobel Prize in Physics.

       In addition to his technical work, Bridgman wrote several books and papers about the philosophical concepts behind the work of scientists. He recognized that the discoveries of relativity and quantum phenomena generated a crisis in the community of physicists, requiring a review of concepts as basic as meaning, the nature of knowledge, and the place for the human being in the universe. In 1926, Bridgman published his book The Logic of Modern Physics, in which he presents an analysis of the new views of physical concepts brought about by the newly developed theories of relativity and quantum physics. As part of this review, Bridgman developed a theoretical concept known as Operational Analysis, which has a very strong pragmatist basis, therefore indicating the possible influence from William James. (Bridgman, 1955, p. vii).

       As described by Holton (2002), Bridgman had a “deeply rooted affinity with the American empiricist philosophers. Here too, was the source of his sympathy with the philosophy of the displaced Vienna Circle, as brought by refugee scientists and philosophers who began to come to the United States in the 1930’s (p. 4).

William James

       William James was a professor of psychology at Harvard from the early 1870’s until his death in 1910. He was the most influential psychologists in the history of the field and is considered the father of American psychology. James was a philosopher and a very prolific author as well, who wrote extensively about many subjects regarding mind and body, religion, and other scientific and non-scientific topics. It is considered that James’ work marked the real beginning of our age of neurophysiology and neurobiology (Richardson, 2010, p. 1). James did extensive studies on consciousness, and he is one of the two founders of pragmatism.

       As described by Richardson (2006), there are at least three reasons to remember James: First, he was a scientist, a medical doctor, working as an experiential physiologist and psychologist, performing experimental work at the laboratory. On this role he was key in developing the modern view of consciousness, in parallel to Freud’s work on the unconscious. He did extensive research in how the mind works, and how mental states are connected to bodily states that can be demonstrated experientially. James second role was as a philosopher, being one of the main figures in the concept of pragmatism, which places more interest in the “fruits than in the roots of ideas and feelings” (p. 5). And the third of James’ roles was that of writer, particularly about religious studies. His book, The Varieties of Religious Experience was the founding text of the modern studies of religion. In this book, James points out that the religious source resides not in books, bibles, buildings, creeds, prophets or popes, but in the individual’s religious experiences, which vary from person to person and from culture to culture. This work by James is attributed the inspiration behind the foundation of the Alcoholics Anonymous movement. (p. 6).

      James was influenced by reading about chemistry and physics when he was a student, and he became interested in the concepts of energy and force, which he used later as part of his research about consciousness and the development of his “radical empiricist” ideas, which argue against monism and materialism. James was particularly interested in the works of the German physicist Gustav Fechner, the founder of psychophysics, which studied the empirical measurement and correlation of mental states with sensory experience (Hawkins, 2011, p. 1).   

Charles S. Peirce

      Another potential link between Bridgman’s philosophies and pragmatism can be found in the similarities with Charles S. Peirce’s works. Peirce was according to James the first creator of the philosophy of pragmatism, and he believed that the meaning of thought is the production of belief, in which beliefs are “rules for action” therefore allowing us to evaluate actions much better by their results than by their origins (Richardson, 2010, p. 183). Peirce was a close friend and collaborator of James, it is believed that it was Pierce who persuaded James to give up medicine and enter into the field of psychology. While Peirce was not part of Harvard’s faculty, two of the most important lectures that he gave in his career were held at Harvard in 1898 and 1903, this last one dedicated to the concept of pragmatism (Houser, 2010, p. 40).

       Peirce had a difficult life due to inner instability and neurotic traits which prevented him from having a consistent academic career, but yet his work is considered a set of guiding principles for a large number of philosophers (Konvitz & Kennedy, 1960, p. 79).

Bridgman’s Philosophical Background

       Bridgman became interested in the philosophical concepts regarding the “existence of things” since he was a student at Harvard. Between 1902 and 1904, he took, or at least audited, courses on the History of Philosophy and Metaphysics: ‘The fundamental problems of theoretical philosophy’ given by Santayana, assistant professor to William James, and also, the course ‘Philosophy of Nature’, taught by James, was offered every year while Bridgman was an undergraduate student. He did not officially registered for these courses; he only formally took the course on ‘General Introduction to Philosophy’ between 1902 and 1903, which assigned James’ Psychology, The Briefer Course, as one of the textbooks. (Moyer, 1990, pp. 246-247).

       Bridgman was a Harvard physics student, with clear interests in the philosophy regarding the nature of reality, at a period in which Harvard had three of the main pragmatists of all time: William James, C.S. Peirce, and John Dewey. James being the most popular of them, so this points out to the probability of Bridgman having the opportunity to have actual contact with James and his philosophy. James B. Conant cites: “to what extent William James’ interpretation of the ideas of Peirce may have subtly influenced a young physicist in the early 1900’s no one can safely say. Of direct connection there is no evidence as far as I can tell but one may be permitted to believe that the intellectual atmosphere which a man breathes when he is young may have influences of which he himself is quite unaware.” (Moyer, 1991, p. 246)        

Philosophical Concepts

       One of the main tasks that Bridgman had in his career, was to analyze and try to solve the difficulties brought about by relativity and quantum physics, which require great attention to the concept of ‘factuality.’ In the first phase of the development of human knowledge, facts were always experienced, as far as an individual observer was concerned, always assuming that the observer was a reliable point of reference. The conceptual discrepancies brought to physics by relativity and quantum theory motivated Bridgman to formulate “something approaching more closely to a systematic philosophy of all physics which shall cover the experimental domains already consolidated as well as those which are now making us so much trouble” (Moyer, 1991, p. 237).

       As part of Bridgman’s effort to give an operational view to the new theoretical knowledge introduced by relativity and quantum physics, he appears to have used several philosophical elements in line with pragmatism, reflecting about the meaning of things, the nature of the observer, and the definition of concept. He also did extensive work of operational analysis in the field of thermodynamics.

Pragmatism

       In his book, Reflections of a Physicist, Bridgman (1955) published a collection of  his main papers, and in the introduction he describes how “The operational approach will be found explicitly and consciously in a number of the papers, but I think that it is implicit on all of them, and that none of them could have been written before I become operationally self-conscious.” (p. viii). Bridgman describes how he realizes that he is using a “new way” in how he handles his mind, and he recognizes that his thinking has a “different feel”. The analysis of the process that made Bridgman “operationally self-conscious” and change the way he felt about his thinking is of major importance to determine the possible influence that pragmatist philosophies might have had on him.

Meaning      

       In many of his works, Bridgman focuses a great effort in discussing the concept of meaning, which James does as well as part of his psychological writings. Bridgman approached the concept by describing how in order to know the meaning of a term it is required to know the conditions under which the term will be used, therefore making this an analysis of operations that conclude that meanings are operational. He indicates that “unless one knows the operations one does not know the meaning” and “what a man means by a term is to be found by observing what he does with it, not by what he says about it” (Bridgman, 1955, p. 4). All these are profoundly pragmatic ideas, that describe how actions or “operations” as Bridgman describes, are the important aspects when describing any type of condition.

       These ideas by Bridgman have great resemblance to the pragmatic views by Peirce. Houser (2011) describes Peirce’s emphasis on the “conceptual groundedness of pragmatic meaning”, and quotes: “Our conception of an object involves our conception of effects which might conceivably have practical bearings. Meaning concerns the relation of objects to experiential consequences, to be sure, but it does so only in the context of a network of conceptions or beliefs.” (p. 44).

       Konvitz & Kennedy (1960) also find Bridgman’s operational analysis model in line with Peirce’s definition, in which Peirce works his definition in terms of the behavior of the object of our conception, while Bridgman “by formulating his as an activity of the subject who is doing the conceiving, in effect points out a necessary presupposition of Peirce’s statement. The two definitions are complementary.” (p. 282).

The Nature of the Observer

       Bridgman (1955) describes that the operational method requires the participation of an observer, or a “performer of the operations.” He indicates that this needs to be a “human performer” so that “the nature of meaning itself makes it impossible to get away from a reference system (the operator)” (p. 111). This concept is in line with the role of the observer in quantum physics, and is in conflict with Einstein’s General Theory of Relativity which eliminates any measurement reference. It is also compatible with James’ views on the nature of reality, which he relates to the ego, as described by Richardson (2010) quoting James: ”Reality, starting from our ego, thus sheds itself from point to point – first, upon all objects which have an immediate sting of interest for our ego in them, and next, upon the objects most continuously related with these. It only fails when the connecting thread is lost” (p. 57). This is an important concept raised by James, in which our ego is essential for the existence of reality, and at the same time, describes a connection among all things in the world in order to build reality.

       Bridgman (1958) describes how, in the context of quantum theory, “the observer is highly specialized and is essentially the measuring instrument”. He makes the point that quantum theory makes us realize that we cannot have information without the use of some method, requiring us to explain “what we know and how we know it”, making us remember that we always need an observer, and this observer is ourselves, with no opportunity to get away from ourselves, even if humanity has been trying to get away from itself ever since humans “started philosophizing and worshipping” (p. 88).

Concept

       Bridgman developed his method of operational analysis as a way to deal with the context of the conceptual revolutions that modern physics theories were generating in the early 1900’s. The main shift of thinking created by these theories was the change from taking concepts as descriptions of the properties of objects to taking concepts as descriptions of the activities of the researcher, therefore, as an example, length and velocity are achievements of the activity of humans on the world, and not direct properties of the world. In this approach, the concepts are not fixed items, but are constantly changing in reference to the changes that are introduced by the evolution of measurement and experimental techniques that humans are using to observe the physical world. Bridgman believed that with the introduction of Einstein’s Special Theory of Relativity the criteria on which concepts were based was changed by “showing that the meaning of a concept was relative to the physical operations of the observer in determining its values and conditions of occurrence” (Ribes-Iñesta, 2003, p. 112).

       Bentley (1938) describes that concept is something that a physicist has or does, and involves empirical experiencing. “Operation and concept, therefore, exhibit the characteristics of a common psychological world and a common empirical world, so that some real possibility exists of development in a common system. They represent, nevertheless, different phases or aspects, of the types most commonly spoken of as ‘fact’ and ‘knowledge of fact.’ For the term ‘concept,’ its extension, the range of its meaning, is plain enough in Bridgman’s use; the sum total of concepts is the sum total of knowledge existing at any time” (p. 140). Bridgman concludes that “New experience can demand only an extension of previously held concepts, not a fundamental revision” (Bridgman, 1980, p. 9).

Thermodynamics and Human Limitations

       Classical thermodynamics provided Bridgman with the best example of operational attitude, representing the most general principles in all of science, and describing the necessary conditions to which all other branches of science need to align. Thermodynamics helped Bridgman to affirm his moral position. Given that the first law of thermodynamics (the conservation of energy) determines that perpetual repetition of mechanical motion cannot produce any useful work, and the second law (entropy) indicates that it is impossible to make a cyclically operating machine that returns repetitively to its original condition without having outside work done on it, these laws therefore summarize the limits of human ability to exploit natural motion (Walter, 1990, p. 225).

       Bridgman (1941) says: “It must be admitted, I think, that the laws of thermodynamics have a different feel from most of the other laws of the physicist. There is something more palpably verbal about them – they smell more of their human origin. The guiding motif is strange to most of physics: namely, a capitalizing of the universal failure of human beings to construct perpetual motion machines of either the first of the second kind. Why should we expect nature to be interested either positively or negatively in the purposes of human beings, particularly purposes of such an unblushingly economic tinge?” (p. 4).

Research Question

      How much influence did the field of psychology had on modern physics, particularly in regards to the works of quantum physics? Did the work and philosophy of William James, and potentially of other pragmatists, have an influence in the development of P.W. Bridgman’s work and some of his Harvard students, like J.C. Slater? Is there evidence of a potential connection to Niels Bohr and his Copenhagen team to James via the Harvard physicists of the time?  

Rationale

       The development of early 20^th century physics and psychology seem to have several analogous implications. On one side, psychology has found in the depths of the psyche a very strong connection to matter, and physics has found a strong connection of matter with psyche. While the nature of these connections remain unknown and elusive, the possibility of transcending the dualism of mind and matter gives motivation to develop a more unified view of the universe (McFarlane, 2000, p. 2).

       Another connection between psychology and physics is described by von Franz (1992), who writes about the concept of matter and psyche from the point of view of Jung’s psychology, describing Jung’s concept of the unus mundus, psyche and matter in alchemy and modern science, and discussing the history of the development of synchronicity, and the concept of time in psychology. Von Franz also writes that “the notion of complementarity introduced by Niels Bohr to provide a better explanation for the paradoxical relationship between waves and particles in nuclear physics can also be applied to the relationship of conscious and unconscious states of a psychic content, This fact was discovered by Jung, but it was particularly elaborated by Wolfgang Pauli. (Von Franz, 1992, p. 246).

Learning Objectives

      The main objective of this research is to understand one more possible way in which the field of psychology could have influenced the development of modern physics by the introduction of the pragmatism philosophy of William James and others into the philosophical concepts used by P. W. Bridgman in his work as a physicist, identifying a new possibility of connection to the work of Niels Bohr in Quantum Physics.

Literature Review

       Beller’s book covers the scientific dialogues that occurred around the development of the quantum theories, particularly in regards to the development of the Copenhagen Interpretation of quantum physics. It is an historian’s view of the evolution of quantum ideas, describing the different actors and their interrelation. The book discusses the Bohr-Kramers-Slater work on the Compton Effect and provides a description of the similarities between Bohr and James’ views on the concept of wholeness and its relation to quantum entanglement or inseparability. It also discusses the comments of John Slater about Bohr’s work style, more based on an intuitive, “analogy-based” approach to science, than following mathematical formalism.

       Bentley’s paper Physicists and Fairies is a description of how the works of physicists and psychologists are drawing closer given the increase of the difficulty of the new problems of science. Bentley states that psychologists deal with a world of fairies, spirits and spooks, reminiscent of the work of alchemists, and then proceeds to analyze the concept, as one particular “spook” that requires clarification. The paper provides a detailed discussion of what are facts, and how facts are used in the physical interpretation of the world. In describing the work of physicists when being faced with fairies and spooks, Bentley enters into a detailed description of the works of P.W. Bridgman and Margenau.

       In the book The nature of thermodynamics, Bridgman analyzes the concepts of thermodynamics, such as the concept of energy in the first law and the concept of entropy in the second law, through his operational method. He describes the way that these laws behave at the macroscopic level, and theorizes about their implications at the atomic levels.

       Bridgman’s Reflections of a Physicist is a compilation of most of his non-technical papers. Most of these papers were written after 1923, and they cover in great detail Bridgman’s points of view on Operational Analysis, the operational aspect of meaning, and the application of these philosophical concepts to the scientific evolution of the time. Bridgman also writes about his struggle with Einstein’s theories of relativity and tackles some humanistic concepts like the social responsibility of scientists, materialism and human spirit, and intellectual integrity. In this book, Bridgman also presents some prophetic ideas about the evolution of intelligence and the future place for science.

       Bridgman’s article Quo Vadis, published in Daedalus in 1958, rejects the general opinion that the sciences and humanities are in conflict with each other, identifying the need to recognize that each one’s portion of the world view is incomplete, requiring to have interest and sympathy with each other, and re-establishing a learning community that recognizes the binding need of paying attention to the integrity of each individual concern.

 The book Philosophical writings of Percy Williams Bridgman, consists of two of Bridgman’s major philosophical works, The Nature of Physical Theory, written in 1936, and The Nature of Some of our Physical Concepts, written in 1952.  The Nature of Physical Theory is an expanded work based on three Vanuxem lectures held at Princeton University in December of 1935, in which Bridgman tackles the possibilities of experimental physics in regards to the recent developments of physics of the time. He acknowledges the increased complexity of the “purely factual knowledge” of the time, and the intense theoretical development of ideas. He also continues to discuss the operational meaning approach to science, and even covers some philosophical views about the use of thought, language and logic, in the work of science. In The Nature of some of our Physical Concepts Bridgman discusses Einstein’s Special Theory of Relativity and Quantum Mechanics from the standpoint of Operational Analysis. It provides an expanded view from the work presented in The Logic of Modern Physics about some concepts like empty space, and the nature of light, using the operational approach from the instrumental and verbal component views, in the study of thermodynamics and electromagnetism.

       Favrholdt’s book Niels Bohr’s Philosophical Background provides a summary of Bohr’s biography, and discusses Bohr’s early studies in psychology, such as his participation in the group called “The Ekliptika-circle”, which had great philosophical influence from Hoffding. The book provides great details about the possible sources of Bohr’s philosophy, and while focusing mostly on Hoffding, it tackles what the author calls the “myths” of Kierkegaard, James and Hoffding, trying to debunk the ideas that these three philosophers could have influenced Bohr in his work on quantum physics. In summary, the author offers the thesis that Bohr did not have any strong external influence that impacted the result of his work on the Copenhagen Interpretation of quantum physics, but mostly acted from his own original ideas.

       Hawkins paper describes some aspects of the influence that the physicist Gustav Fechner had on his works, particularly in regards to the transmission theory of consciousness, and the related concept of the compounding of consciousness. It provides a view of the evolution of James philosophy since his days as student in Germany, under professors Wundt and Helmholtz, going from an earlier dismissal by James of Fechner’s philosophies in his book Principles of Psychology (1890), to a later support and adherence to Fechner’s ideas by the time James wrote A Pluralistic Universe in 1904.

       Holton’s paper The Roots of Complementarity provides a detailed description of the formulation of the Principle of Complementarity by Niels Bohr, with an historical context that describes the historical evolution of the ideas prior to Bohr’s 1927 conference in Como, Italy, when he described the principle for the first time. Holton brings up the possible connection to William James philosophy, and describes in detail the interview by Kuhn and Petersen to Niels Bohr one day before Bohr’s death, in which interview Bohr mentions having read the works of William James, particularly The Stream of Thought, without giving much detail as to when exactly Bohr did read James works, but only indicating that this happened about the time when Bohr was working on surface tension, which Holton assumes that could be around 1905.  

       In his book Thematic Origins of Scientific Thought: Kepler to Einstein, Holton gives an historical view of science using a “thematic” content, rather than an empirical or analytical approach. He pays great attention to what he calls “the nascent phase”, described as “the interval of science-in-the-making before the finished work is assembled and, more often than not, is made to look inevitable.” Holton dedicates one full chapter to the topic of Bohr’s Complementarity and its roots, and provides the description of potential influence by James as he does in his 1970 paper. As part of a chapter on the quantum physics research in the United States, he describes Bridgman’s activities regarding the evolution of the theoretical work in physics at Harvard.

       Holton’s paper Candor and Integrity in Science gives a description of the way scientists rely on the truthfulness that researchers need to embrace in order to maintain credibility in science. The paper gives Holton’s personal experience working with P.W. Bridgman, first as his dissertation student in experimental physics, later as a colleague, and finally, after Bridgman’s death, as the person responsible to archive his laboratory notebooks and papers. The second half of the paper is dedicated to give a clear picture of the integrity that Niels Bohr demonstrated in his scientific work, as well as in all aspects of his life, including his efforts regarding world peace after the end of World War II.  Holton describes the efforts of Bohr of expanding the concept of complementarity to the fields outside physics, such as biophysics, and mainly to the understanding and toleration of differences between traditional cultural systems.

       Houser’s paper discusses the philosophical connection between Peirce and James, describing their views on pragmatism, their differences and similarities. It provides a chronological description of their parallel careers and friendship, and raises questions about how much they influenced each other intellectually, what did they learn from each other, and how did they help in shaping each other’s ideas. This paper also references Bridgman’s operational account of meaning, and its similarities to Peirce’s pragmatic views.

       James’ book The Principles of Psychology summarizes a great part of his most influential and transformational work. It is based on his classroom lessons first published in 1890, and covers many topics such as the functions of the brain, mind-body relationship, thought, consciousness, association, the concept of time, sensation, emotion, imagination, perception of reality, instinct, etc. Bohr references the chapter titled “The Stream of Thought”, which talks about the continuity of consciousness, the substantive and transitive parts of consciousness, and the thought stream, as having been important in his philosophical view that resulted in the development of the Principle of Complementarity.

       William James’ Writings 1902-1910 are a compilation of several of his works, including The Varieties of Religious Experience, Pragmatism, A Pluralistic Universe, The Meaning of Truth, Some problems of Philosophy and Essays. In the section about pragmatism, James deals with the concepts of truth, the one and the many, the growth of knowledge, the mental evolution, and pragmatism and humanism, which can be directly related to the concepts used by Bridgman in his operational method.

       Konvitz & Kennedy book, The American Pragmatists, is a collection of selected writings of the main group of American pragmatists, including Emerson, Peirce, James and Dewey. This collection of writings is examples of pragmatist application on religion, metaphysics, science, education and social philosophy. This book includes a chapter on Percy W. Bridgman, who while being a physicist, is considered a philosopher that according to Konvitz & Kennedy belongs in the distinguished group that includes Mach, Poincare, Einstein and Born.

       Kremble and Birch’s book provide a biography of Percy Williams Bridgman, focusing on his career at Harvard, and his work on experimental physics, mainly in the field of high pressures. It provides a complete bibliography of Bridgman’s works in chronological order.

       Kuhn and Van Vleck’s interview with Dr. John C. Slater covers his biography, his student days and his professional career. It covers in great detail questions about the type of readings that Dr. Slater did, the seminars he attended, and the scientists of the time that were of Slater’s most interest while he was a student at Harvard. He describes how he chose Dr. Bridgman to be his thesis advisor after having worked as Bridgman’s assistant for two years, and how Bridgman suggested that he dedicated his career to theoretical physics. Slater also discusses his experiences working with Bohr in Copenhagen, and details about the development of quantum theory, including details about the collaboration with Bohr and Kramers in the writing of the “BKS” paper about the Compton Effect.

       McFarlane’s paper provides a very simple description and background of the main concepts of quantum physics and Jungian psychology, trying to identify the similarities and parallel ideas among the two fields of knowledge. It provides a clear definition of the concept of Complementarity from the point of view of wave and particle. It has a chapter dedicated to the analysis of psyche and matter and the connections between them, providing a summary of the correspondence between complementarity principles in psyche and matter. From the psychological standpoint, the paper approaches the concepts of archetype, logos, the ego, and Jung’s concept of the unus mundus.

       Moyer’s paper P.W. Bridgman’s Operational Perspective on Physics provides a detailed description of the origins and development of Bridgman’s operational method. It describes the background details regarding Bridgman’s student years, his studies at that time, and the philosophical influences that he received. The paper provides details about the psychology and philosophy classes that Bridgman could have taken and audited during his undergraduate years, and later the approach taken by Bridgman towards Special Relativity and Dimensional Analysis.

       In the book William James, In the Maelstrom of American Modernism, Richardson writes an intellectual biography of James, trying to understand his life through his work. It provides an extensive view of James works on consciousness, psychology and religion, and performs a deep analysis in James’ role as a philosopher.

       Ribes-Iñesta’s paper describes the influences of S.S. Stevens’ and P.W. Bridgman’s operationism on psychology, as well as the role of operationism on the scientific method. The paper provides a comparison of Stevens and Bridgman’s views on operational theory and how these views influenced the work of B.F Skinner. It describes a summary developed by Houts on the relevance and context of Bridgman’s operational analysis and his debate about Einstein’s Special Theory of Relativity in regards to the meaning of a concept and the role of the observer. The paper also discusses how Bridgman provides a pragmatic view of operationism, while Stevens approaches the concept with a basis on semantics. The conclusion given by this paper is that Skinner’s work received the most influence from Stevens’ philosophy, rather than from Bridgman’s.

       Richardson’s book The Heart of William James provides a brief biography and a summary of some of the most important pieces found on the nineteen-volume The Works of William James published by Harvard University Press between 1975 and 1988. Some of the most important subjects related to this study include the chapter on The Perception of Reality, in which James analyzes the concepts of belief, the various orders of reality, the many worlds, the influence of emptions and impulses on beliefs, and the belief in objects of theory, and the chapter on Philosophical Concepts and Practical Results, based on a talk given by James at Berkeley, CA in 1899, and is the basis for his work on Pragmatism published in 1907.  In this chapter, James analyzes Peirce’s philosophy on soul and meaning of thought, our thoughts and conceptions of an object, and the impact of the object’s positive significance, and describes the principle of Peirce, as the Principle of Pragmatism.

       In Psyche and Matter, von Franz writes about the concept of matter and psyche from the point of view of Jung’s psychology, describes Jung’s concept of the unus mundus, psyche and matter in alchemy and modern science, and has a detailed discussion in regards to the history of the development of synchronicity, and the concept of time in psychology.

       Walter’s book provides a detailed biography of Percy W. Bridgman, including his family, educational and religious background, and going through his career as a physicist involved on a field that was going through a major evolution. The book describes Bridgman’s strong work ethics and structure in the importance of the experimental and measurement methods as the building blocks of physical reality. It also describes Bridgman’s strong reaction against Einstein’s change of point of view towards the place of human beings and human experience from the Special Theory of Relativity to the General Theory of Relativity, which eliminates physical objectivity from the concept of space and time. Walter’s book also describes Bridgman’s thoughts regarding quantum physics and the nature of the observer, as well as dedicates a chapter to the field of thermodynamics, which is essential to the connection with the philosophical views of the objective universe.

Method

      The research method to be used for this study will be historical and archival analysis. The strategy will be to request permission to perform research at the archives of William James unpublished works at Harvard University, as well as archives of Neils Bohr works. There is also the possibility to identify relevant correspondence between the main participants in the fields of psychology and quantum physics. The joint work of Jung and Pauli, as well as the correspondence between them and between Pauli and Marie-Louis von Franz will be used as reference only, having the main focus in the direct or indirect interaction that could have occurred at the philosophical level between William James and P. W. Bridgman, identifying potential connection to the works of Neils Bohr and his Copenhagen team.

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