What Does Quantum Mechanics Mean?

Sorry, I don't know. And neither does physicist Alan Sokal:

Sokal did have a “philosophically-oriented approach to physics,” which contrasted with the “very pragmatic anti-philosophical point of view” of many of his colleagues, of which “the extreme version is ’shut up and calculate’: physics is about predicting, experiment and that’s all. I was always opposed to that point of view. It seems to me that physics is about trying to understand the world, and experiments are tools for checking whether your theories about the world are possibly right but they’re not an end in themselves. So I always took an attitude towards physics where I was interested in the fundamental conceptual questions, closer to Einstein’s approach than Feynman’s.

“You can even see this shift in the history of physics a little bit, from the generation of Einstein and Bohr and Heisenberg, who spent a lot of time arguing about fundamental conceptual questions, primarily about quantum mechanics; to the generation after, of Feynman and his contemporaries, who said we can argue about conceptual things until hell freezes over, but there are so many new things to explore in elementary particles, in quantum chemistry, let’s do that. That also coincided with a geographical shift from European dominance to American dominance.

“I don’t criticise the newer generation. They were right that there were so many interesting things to learn and maybe the philosophical discussion had stalled. Nevertheless, it seems to me that the conceptual questions are also fundamental. For example, what does quantum mechanics actually mean? I’ve been using quantum mechanics for about 35 years, almost three-quarters of my life, and the more I study it the less I understand it. So I can understand why a whole generation of physicists threw their hands up in despair and said ‘let’s just calculate’, but that’s not to me a satisfactory final answer.”