From time to time, we hear physicists claim that Einstein didn’t understand Quantum Mechanics and therefore wasted his time with naive classical theories. I very much doubt that this is true. His arguments against Quantum Mechanics were extremely subtle, culminating in one of the most profound and most cited papers in all of physics.12 My guess is that Einstein was disturbed by the same thing that bothered the slow student. How could the ultimate theory of reality be about nothing more concrete than our own degree of surprise at the outcome of an experiment?