As well as providing a bit of intellectual history, this fascinating article in Physics Today demonstrates how Einstein, habituated to thinking philosophically - that is sharply - about what could be known, reasoned his way past the limits of strict empiricism and its rejection of a role for the knower in understanding nature. By doing so, he ultimately produced notions like "entanglement" in quantum mechanics, which are deeply paradoxical, even though he believed the very idea suggested his work was incomplete.
From the article:
Missing from the empiricists' picture was what Einstein thought most important in creative theoretical physics, namely, "free inventions" by the human intellect. Not that the theorist was free to make up any picture whatsoever. Theorizing was constrained by the requirement of fit with experience. But Einstein's own experience had taught him that creative theorizing could not be replaced by an algorithm for building and testing theories.
Einstein chose general relativity over rivals equally consistent with the evidence because its physics plus non-Euclidean spacetime geometry was, as a whole, simpler than the alternatives.
Such questions might seem overly subtle and arcane philosophical issues better left alone. But they cut to the heart of what it means to respect evidence in the doing of science, and they are questions about which we still argue. As theoretical physics moves ever deeper into realms less firmly anchored to empirical test, as experimental physics becomes ever more difficult and abstruse, the same questions over which Schlick, Reichenbach, and Einstein argued become more and more acute.
...Einstein likened crucial aspects of the choosing [of theories] to the weighing of incommensurable qualities' (emphasis supplied).
An "algorithm for building and testing theories?" The suggestion reminds me Nicholas Carr's objection to "writing for machines." In my view language is the summit of cognition, if for no other reason that it can apprehend paradox. Secondly, it reminds me of reductive materialism's denial, or deduction from a closed material systems (think "emergent"),
of first person experience. I'll continue to bet long on the color purple, thank you very much.
How we construe knowledge can and does affect the knowledge we get. By thinking of knowing differently, in the doing of philosophy, Albert Einstein could peer more deeply into the nature of quantum realities than his contemporaries. As science moves ever deeper into the nature of reality, what's known will be new again.