Høffding and Bohr: Waves or Particles

Jan Faye

David Favrholdt

Léon Brillouin

Jan Faye

I: Hoffding as Mentor.- I.- 1. Harald Hoffding, His Life and Thought.- 2. Hoffding and Bohr Senior.- II.- 1. The Ekliptika Circle.- 2. Bohr and William James.- 3. Bohr and Kierkegaard.- 4. The Student Bohr on Formal Logic.- III.- 1. The Friendship.- 2. The Years Around 1927.- 3. Hoffding on Complementarity.- IV.- 1. Hoffding's Theory of Knowledge.- 2. Totality as a Category.- 3. Hoffding's Philosophy of Mind and Psychology of Free Will.- 4. Hoffding on Biology.- 5. Analogy and Scientific Progress.- II: Bohr and the Atomic Description of Nature.- V.- 1. The Principle of Correspondence.- 2. The Search for an Interpretation.- VI.- 1. Complementarity.- 2. Quantum Mechanics and Psychology.- 3. Bohr on Biology.- VII.- 1. The Objectivity of Knowledge.- 2. The EPR Discussion.- 3. The Conditions for Description.- VIII.- 1. Bohr and Realism.- 2. Hoffding on Reality.- 3. Objective Anti-Realism.- Epilogue: The Legacy.- Notes.

Jan Faye, Stefano Furlan, Rasmus Jaksland

John Wheeler tells us that Niels Bohr and Werner Heisenberg met with the Danish philosopher Harald Høffding in the summer of 1927 to discuss the philosophy of quantum mechanics—following the disagreement between Bohr and Heisenberg about the uncertainty relations and right before Bohr’s introduction of his complementarity interpretation of quantum mechanics in Como, Italy, in September 1927. Is this evidence that Høffding had an even greater influence on the early development and interpretation of quantum mechanics than hitherto believed? We trace the historical sources of the story, which Wheeler first heard from Casimir, who apparently was present when the episode took place. We argue that the episode cannot have taken place earlier than 1929 and propose an event in November 1929 as its likely origin. What remains true is that Bohr, Casimir, and Høffding did meet, but the meeting is less remarkable than in Wheeler’s retelling. Nonetheless, Casimir’s role in the story adds new evidence for Høffding’s influence on Bohr. Heisenberg presence, though, is entirely of Wheeler’s invention. We use this rendering to illustrate how Wheeler operated as a storyteller of quantum mechanics from the 1980s to his death.

Hernán Bruno Pringe

In this paper we analyze the historical roots of the Bohrian concept of symbol. More precisely, we argue that Bohr takes Kantian elements from Høffding´s philosophy in order to develop his own concept of symbol. For this purpose, firstly, we focus on the two different senses that Bohr gives to the concept of symbol. Then, we study how each of these senses is related to different aspects of Høffding’s philosophy and we show the connection between the Bohrian and the Kantian concept of symbol by means of Høffding’s mediation.