On the importance of positivism for the quantum revolutions

CHRISTIAN DE RONDE

Buenos Aires

Congreso; II Congreso Latinoamericano de Filosofía Analítica (ALFAn).; 2012

Asociación Latinoamericana de Filosofía Analítica

With the rise of philosophy, the Greeks placed the fundament of thought in the external Cosmos; knowledge of the physical world could then be achieved through contemplation. With the advent of Newtonian Mechanics and its empirical achievements, philosophy posed the problem of justification of a physical theory as true knowledge, episteme. Both rationalists and empiricists attempted to provide an answer to this question. The analysis of David Hume would then expose the problem in all its depth. But it was Immanuel Kant who was able, in his Critic of Pure Reason, to present an architectonic which would lay the new foundations of philosophical thought and objectivity itself. In order to overcome the problem of justification of the relation between ‘object’ and phenomena, Kant developed a philosophy in which the notion of object was not an external aspect of discovery but rather part of an internal scheme through which the transcendental subject was able to bring into unity the chaotic sensations of experience. According to Kant, objectivity came from the interplay between object and the subject. It is the transcendental subject and the way through which he experiences, in terms of the a priori categories and forms of intuition (Newtonian space and time) that the object is brought into stage. Kant wanted to overcome the metaphysics of his time, which according to him had turned thought into dogma. His critical analysis attempted to place philosophy in the secure path of science, exposing the limits of human knowledge. However, his own scheme of thought would be very soon turned itself into new (metaphysical) dogma. The a priori categories and forms of intuition through which Kantian philosophy had constrained physics were questioned and criticized at the end of the 19th century. From the ashes left by this crisis, at the beginning of the 20th century, two physical theories —relativity theory and quantum mechanics— emerged in this new region of thought. It is clear that in order to understand the creation of quantum mechanics, one would need to provide an analysis that is not limited to physics. The crisis in the foundations at the end of the 19th century manifested itself in many fields of human knowledge. Science, philosophy and art expressed in different ways the most important crisis in metaphysical thought, a crisis that had in its kernel the problem of representation and language. The 20th century witnessed both the crisis of metaphysics and the parting of the ways between two seemingly distinct philosophical perspectives, what has been known as the analytic school of thought and continental philosophy (Friedman 2000). Regardless of their differences, both philosophies have shown a deep interest in the relation of language to reality. Some call this new period, in which the fundament of thought has been related to language itself ‘the linguistic turn’. Within philosophy of physics the crisis was exposed through the tension between the classical conception of an objective physical reality and what was taught by quantum theory. Although there have been many proposals to solve this problem there is no consensus neither in the scientific nor philosophical community regarding even the possibility of such a solution. In this work we are interested in showing that the discussion between Einstein, Bohr, Pauli and Heisenberg was focused in the problems posed by metaphysical and anti-metaphysical positions regarding the meaning and understanding of physical reality, the role played by concepts and language within physical theories and the consideration of what is meant by a ‘physical situation’. In this sense, we shall call special attention to the importance of positivism within the quantum revolution and its relation to the subsequent discussions of the founding fathers. Already in the mid 19th century criticism of metaphysics had appeared explicitly in the positivistic philosophy of the French Auguste Compte and the British John Stuart Mill. Positivism derived from Enlightenment thinkers like Pierre-Simon Laplace and many others, but was firstly systematically theorized by Compte, who saw the scientific method as replacing metaphysics in the history of thought. Positivism states that the only authentic knowledge is knowledge that is based on actual sense experience. Such knowledge can come only from affirmation of theories through strict scientific method. Metaphysical speculation is avoided. In particular, Mach’s critical positivism played a significant role within the scientific revolutions that took place at the beginning of the 20th century. After some centuries, the categories and forms of intuition had become exactly what Kant had striven to attack in the metaphysics of his time, dogmatic and unquestionable elements. Kant had fought 17th century metaphysics, but his own philosophy had turned itself into new dogma. As noted by van Fraassen (2008, p. 2): “Kant exposed the illusions of Reason, the way in which reason overreaches itself in traditional metaphysics, and the limits of what can be achieved within the limits of reason alone. But on one hand Kant’s arguments were not faultless, and on the other there was a positive part to Kant’s project that, in his successors, engaged a new metaphysics. About a century later the widespread rebellions against the Idealist tradition expressed the complaint that Reason had returned to its cherished Illusions, if perhaps in different ways.” Ernst Mach is maybe one of the most influential positivistic thinkers of the 19th century. His ideas and criticisms are deeply engaged with the development of physics that took place at the beginning of the 20th century. His investigations led him to the conclusion that science is nothing but the systematic and synoptical recording of data of experience. In close analogy to Darwinistic ideas Mach conceived the evolution of knowledge in physical theories as a process of “struggle for life” and “survival of the fittest”. In his Analysis of Sensations, Mach concluded that primary sensations constitute the ultimate building blocks of science, inferring at the same time that scientific concepts are only admissible if they can be defined in terms of sensations. Although Mach had been himself a neo-Kantian, within his neo-positivist conception of science, he stated that we should reject every a priori element in the constitution of our knowledge about things. Science would be then nothing but a conceptual reflection of the facts provided by sensations. Scientific propositions should be empirically verifiable and as a consequence, within this doctrine there is no place left for a priori concepts. The incisive criticism of Mach on the lack of foundation of the physical concepts in the theories of his time allowed a complete reformulation of the meaning and applicability of physical concepts. It is well known that the philosophical ideas of Mach had a great influence on the development of special and general relativity. Albert Einstein indicated on several occasions the relations of his own ideas to those of Mach, in whom he recognized a guide. Moreover, the importance of Mach’s thought should not be underestimated in relation to the development of quantum theory. As noticed by Charles Enz (1985, p. 250): “Clearly, positivism played an important part in the creation of quantum mechanics as is evident, e.g., from the letter [93] by Heisenberg to Pauli quoted in Ref. 16. And, as mentioned earlier, Pauli never refuted his positivistic argument about the relation between field strength and test charge contained in his third paper of 1919.” Heisenberg also discussed together with Einstein and Pauli the relation between Machian philosophy and the ontological and epistemological constitution of atomic theory. The richness of this debate, which comprises several questions such as the meaning of observation, the question of pragmatics, realism and the problem of interpretation can hardly be underestimated (see Heisenberg 1971, pp. 63-66). As we shall argue, the importance of Mach’s positivistic ideas regards not only the deconstruction of Kant’s a priori architectonic but also the possibility of the constitution of a new experience. His analysis opened small cracks in the basic physical presuppositions connected with the metaphysics of his time, and so, prepared a period where those who followed were able to go beyond the presuppositions and impositions of classical physics. Only after Mach and his criticism of the a priori; the concepts of ‘space’, ‘time’, ‘substance’, ‘causality’, etc. could be discussed and deconstructed one by one opening at the same time the doors of new concepts. The Machian epistemological principle had broken the chains of the fixed Kantian a priories. 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