April 1999, “Thinking Kantian Thoughts?” The other day I wrote the little essay below [cf. “Fuchsian Genesis” addressed to Greg Comer, dated 22 April 1999] for myself, and then searched up a reason to send it to my friend Greg Comer. It would have been better to send it to you I think. It strikes me as sounding a little Kantian, though with an extra twist: namely, that we are even further removed from the “ding an sich” than he had imagined. On my view, we know that the quantum formalism CANNOT correspond to reality (whatever it may be). My understanding of Kant is that he would have said that classical physics may or may not be a reflection of the real thing, but we can never know. It does form part of the categories of understanding and is therefore necessary to make sense of the world; but correspondence to reality is a different issue – in fact, one that cannot be decided. In the case of the quantum world, I think it is (reasonably) safe to assume that the terms in quantum theory cannot be mapped to any sort of “ding an sich.” That's why it strikes me as a still stronger form of Kantianism. Am I way off track here? Any thoughts? Jon's Reply Chris said: My understanding of Kant is that he would have said that classical physics may or may not be a reflection of the real thing, but we can never know.
April 1999, “Thinking Kantian Thoughts?” The other day I wrote the little essay below [cf. “Fuchsian Genesis” addressed to Greg Comer, dated 22 April 1999] for myself, and then searched up a reason to send it to my friend Greg Comer. It would have been better to send it to you I think. It strikes me as sounding a little Kantian, though with an extra twist: namely, that we are even further removed from the “ding an sich” than he had imagined. On my view, we know that the quantum formalism CANNOT correspond to reality (whatever it may be). My understanding of Kant is that he would have said that classical physics may or may not be a reflection of the real thing, but we can never know. It does form part of the categories of understanding and is therefore necessary to make sense of the world; but correspondence to reality is a different issue – in fact, one that cannot be decided. In the case of the quantum world, I think it is (reasonably) safe to assume that the terms in quantum theory cannot be mapped to any sort of “ding an sich.” That's why it strikes me as a still stronger form of Kantianism. Am I way off track here? Any thoughts? Jon's Reply Chris said: My understanding of Kant is that he would have said that classical physics may or may not be a reflection of the real thing, but we can never know.
ENERAL philosophy claims to be the critical subject which lays down for all of us what we may be allowed to think, and yet it has played no part whatever in the great revolutions of human thought of the present century-those connected with relativity and the quantum theory. It might have been expected that the scientists would have been constantly consulting the philosophers as to the legitimacy of their various speculations, but nothing of the kind has happened. Since no one can dispense with some sort of metaphysic, each scientist has made one for himself, and no doubt they contain many crudities, but it would seem that a deep interest in metaphysic is a disadvantage rather than an advantage to the physicist-at least I have the impression that those of my friends who are most inclined to speculate on the ultimate things appear to be the ones whose scientific work is most hampered by doing so. Now I propose to risk a similar indiscretion. I want to embody in it the practical philosophy of a physicist, and I do not mean it as an attack on the pure philosophers, who are very reasonable people, only chargeable with the minor offence of not having made me want to read their books! I had better begin by stating shortly the ideas I intend to discuss. There is a notable contrast between the way we think about things and the way we think we ought to think about them.
22 August 1999, “Your Article” I am writing to let you know that I enjoyed your article quant-ph/9812050, “Why Quantum Mechanics is Hard to Understand,” very much. I was in particular very pleased with your Section IV “Dynamics vs. History.” It may interest you to know that Markus Fierz expressed a similar point of view in his article: “Does a physical theory comprehend an ‘objective, real, single process’?” in Observation and Interpretation in the Philosophy of Physics , edited by S. Körner (Dover, NY, 1957), pp. 93–96. I will append the full text below for your enjoyment. [See note to Rüdiger Schack, dated 29 August 1999.] Most importantly, I would like to ask you for the final coordinates of your paper. Was it published somewhere? I would like to cite it in an upcoming paper. 28 August 1999, “Not Much” I don't have a good idea about where to send your paper. I think chances are that AJP will be tougher than FP . In any case, it had an impact on me. My old advisor used to say of our joint papers, “If three people read this paper, we'll be doing OK!” If you know of two others with yours, you're probably doing OK. I like this focus on the concept of “object.” I look forward to anything you might have to say about it. I have some slides that I use as a rallying cry to the idea that quantum information theory may have some impact on quantum foundations. The first is a list of axioms for quantum mechanics.
The ghost of my father sat in front of me sprinkling salt into its beer. The floor, wooden and sole soaked slick I could just push my feet and rub my fingers. “Give me more life,” I whispered. I wanted to touch the flakes of rust on the cooler, mingled with sweat. Bottle caps everywhere; it didn't understand the boredom. My only sound was that of a screen door. “My son will be a professor of physics in three years.” 14 February 1995, “Turtle Wax” Let me wax just a little. A few quotes by Wolfgang Pauli on quantum mechanical randomness and objective reality. (Taken from the English translation of a paper titled “Matter.”) “Like an ultimate fact without any cause, the individual outcome of a measurement is, however, in general not comprehended by laws. This must necessarily be the case …” “In the new pattern of thought we do not assume any longer the detached observer , occurring in the idealizations of this classical type of theory, but an observer who by his indeterminable effects creates a new situation, theoretically described as a new state of the observed system. In this way every observation is a singling out of a particular factual result, here and now, from the theoretical possibilities, thereby making obvious the discontinuous aspect of the physical phenomena.” “Nevertheless, there remains still in the new kind of theory an objective reality , inasmuch as these theories deny any possibility for the observer to influence the results of a measurement, once the experimental arrangement is chosen.”
January 1999, “The (Un-)Detached Observer” Yesterday I ran across your paper “On the Interpretation and Philosophical Foundation of Quantum Mechanics” posted on the web, and was very much impressed with its depth. Most importantly, however, I am sad to say, it reminded me that I still owe you some papers. I have remedied that now by sending you a pile of things that I have written on the relation between information gain and quantum state disturbance. These are relevant to your request above, and, I think, even more relevant to the thoughts in your paper. I am in great agreement with the idea that there may be a deeper foundation to quantum mechanics, one along the lines that Pauli and Wheeler attempted to sketch. Quantum mechanics, it seems to me, is an expression of the best we can say in a world where the observer is not detached (to use Pauli's phrase). Recognizing and appreciating that lack of detachedness is the most exacting tool we have for peering into the greater future of quantum theory. This I think is the ultimate role of quantum information theory. (For the opposite point of view, however, you may be interested in having a look at John Preskill's paper “Quantum Information: Its Future Impact on Physics” at http://theory.caltech.edu/~preskill/.) I hope you will enjoy the things I have sent you; it is always my attempt to be as clear as I possibly can be when I write.
In the Critique of Pure Reason Kant argues that the empirical knowledge of the world depends on a priori conditions of human sensibility and understanding, i. e., our capacities of sense experience and concept formation. The objective knowledge presupposes, on one hand, space and time as a priori conditions of sensibility and, on another hand, a priori judgments, like the principle of causality, as constitutive conditions of understanding. The problem is that in the XX century the physical science completely changed how we conceive our knowledge of the world. Face to this new situation, what was changed in our classical reason? However, if the transcendental point of view is adopted, in the specific case of quantum mechanics, we have to wonder about the general conditions of this theory that make possible such knowledge, which predictive value is much more accurate than the classical physics. The aim of this work is firstly to show the Kantian implications on Bohr’s interpretation of quantum phenomena and secondly to provide an overview of the key elements for understanding the transcendental locus of ordinary language in the quantum mechanics context, in order to give support to a transcendental pragmatic position in the analysis of science.
12 June 1999, “Interest in Pauli” I have come across a reference to a paper of yours that I have not been able to obtain. May I ask of you to send me a reprint of it? The paper is: C. P. Enz, “Wolfgang Pauli and the Role of the Observer in Modern Physics,” in Philosophy of the Natural Sciences: Proceedings of the 13th International Wittgenstein Symposium , edited by P. Weingartner and G. Schurz (Verlag Holder–Pichler–Temsky, Vienna, 1989), pp. 110–119. I have read several of your other papers on Pauli's thought and have been uniformly pleased with each. I am especially interested in his ideas concerning the demise of the “detached-observer” notion within quantum theory. (I would also be interested in any of your other works on the subject that may have been written since your 1992 article, “Wolfgang Pauli between Quantum Reality and the Royal Path of Dreams.” This is the latest one that I am aware of.) About myself, I am a theoretical physicist at Caltech who specializes in quantum information theory and quantum computing. I am well acquainted with your colleague Nicolas Gisin at the University of Geneva. 21 August 1999, “One More Article?” Upon my return from Cambridge a couple of weeks ago, I found in my mailbox your package full of wonderful papers! Thank you so much.