When it comes to edgy Feynman quotes, I would recommend Angela Collier's "The sham legacy of Richard Feynman".

Short summary: while Feynman was obviously a great physicist who got a well-deserved Nobel prize, he is commemorated for all the wrong reasons. This is mostly due to Leighton's "Surely you're joking Mr. Feynman" which established a mythos around the man with a low fact-basis and which gives its readers a deceptive image what it means to be a good physicist.

Back to the point: The whole "understanding quantum mechanics" has become a trope on physics-related internet forums: usually somebody posts something like you just did, then somebody answers it applying a general definition of "understanding" according to which quantum mechanics is understood, which is followed by either the discussion creator or someone else narrowing down the definition of "understanding" so far that eventually QM drops out of it; strictly spoken, Newtonian classical mechanics quite often wouldn't fulfill these narrowed definitions anymore, either, because you could also ask "do we understand what a force is" until every legitimate physicist just quits annoyedly because on the other side there is evidently no real interest to learn something about physics.

Therefore, you can either waste your lifetime asking such questions on the internet, or you can learn actual physics and at least enter the circle of "people who understand QM according to a general definition of 'understanding'".

P. P. Afxenti Jürgen Weippert

I like to somehow follow on from Jurgen's excellent response.

it’s entirely reasonable to extend the spirit of Feynman’s quote to other branches of physics when considered at the level of deep internal awareness or epistemological blueprinting.

Feynman’s “Nobody understands quantum mechanics” wasn’t just a throwaway line. He was pointing at the disjunction between mastery of mathematical formalism and true conceptual comprehension — a tension that arguably underlies much of physics.

So your question — whether this applies to all of physics when one truly interrogates why and how one thinks about it — maybe..

While Feynman’s quote about quantum mechanics is rooted in the specific interpretational difficulties of that field, your proposition — that a similar epistemic gap exists across all branches of physics — is not without merit, though it requires nuance.

It’s fair to argue that most physicists operate at the level of pragmatic formalism — they know how to make models and predictions, but often lack a meta-theoretical awareness of what those models mean, or whether they truly map onto reality.

This gap becomes more visible when we examine:

• foundational debates in thermodynamics (e.g., what is entropy?),

• the ontological status of fields in classical and quantum field theory,

• or even the nature of spacetime in relativity.

So, while it’s not accurate to say nobody understands classical or relativistic physics the way Feynman meant about quantum mechanics, it is accurate to say that full epistemic and conceptual self-awareness is often lacking across the board — especially when physicists do not interrogate the why behind their methods.

Thus, your interpretation is a legitimate philosophical generalization, even if not precisely what Feynman meant.

Mr Shore,.

My implication is that lack of meta-theoretical awareness of what those models in physics mean, or whether they truly map onto reality, might be a bigger problem than people realize, encompassing all of physics, even the most "obviously understood" principles and models.. By principle, or by my assumptions, if it applies to the best theory (by precisiin, QM) it should Apply to all others and also the underllining blueprint of the science we are talking about

Jurgen,

I asked if you agree or not.

Thanks for the analysis and useful remarks l, however, giving me lessons about whether i need to "start learning physics" is a sign: 1. Lack of understanding of the issue behind the question and misintertreting the thin line towards a self-serving allegatory comment 2. An attempt to appear a Teacher status where here at ResearchGate Nobody is in a Teacher-student relation

Dear Philippos Afxentiou, Yes, this is true for many areas and not only physics. For example, we do not know the true nature of the charge or the reason for the differences in the charge of a positron and an electron, with all other characteristics being the same. But this does not prevent us from creating real systems, as well as conducting real calculations. An exciton is a quasiparticle that does not transfer either mass or charge. But it is used to build models that allow us to evaluate the mechanisms to some extent. Most likely, we will never reach the level of knowledge at the deepest level. I am engaged in materials science - the development of materials with a set of specified properties. The current concepts of quantum physics allow us to develop such materials that work in real conditions and with real characteristics. At the same time, determinism cannot be denied. Our approach must be comprehensive, using the most suitable physical concept for solving practical problems. After all, we must obtain a real material with a set of specified properties and we use all possibilities to achieve this. Best regards, Rustam