"I consider it entirely possible that physics cannot be based upon the
field concept, that is on continuous structures. Then nothing will
remain of my whole castle in the air, including the theory of
gravitation, but also nothing of the rest of contemporary physics."


Like many of Einstein's thoughts, remarkably prescient.

There has been more and more discussion of the Universe being somehow
"digitized", possibly in the form of cellular automata. This would demolish
the field concept, Einstein's theory of gravitation, and all physics done
since Newton (which is all the rest of contemporary physics).

I don't know when Einstein made this observation, but it was certainly
before the development of cellular automata theory. He saw far.