"No one knows anything. The whole affair would have been a delight to Jesuit fathers."
—Albert Einstein on the first international meeting on quantum physics, Solvay, 1911
Albert Einstein (1879-1955) is famous for many things. Mostly, now, he is remembered as the genius who changed scientists' (and other educated peoples') view of the nature of space and time through his theories of Special Relativity and General Relativity.
The second most famous thing about Einstein is that he showed this genius later in life. It is common knowledge that he did poorly in school as a child. This story is beloved by parents who feel their child's self-esteem is more important than actually hitting the books and proving they have done it with good grades. Unfortunately the story is not true. Little Albert's grades were quite good from elementary school to graduate school. [The best Einstein biography for advanced readers, including Philosophy students, is Subtle Is the Lord: The Science and the Life of Albert Einstein]
The third most famous thing about him was his support for the U.S.A. developing an atomic weapon, followed by his regret that an atomic weapon was developed and used to destroy two cities filled with people in Japan. Albert was a peace activist well before World War I began, and remained so until the end of his life.
Albert Einstein was interested in philosophy from at least as early as his college days. Possibly the fourth most famous thing he was famous for was not being able to reconcile with the science of quantum physics, even though he was one of the inventors and major contributors to that branch of science.
Quantum physics developed slowly. Its origin is usually marked by Max Plank's paper on radiation in 1901, which to jump to a later interpretation said that electromagnetic radiation (including light) comes in energy packages, or quanta. This went along with the ongoing development of the atomic theory, which had shown that electric charge also came in packages, which came to be called electrons. There were many weird things about the new theory, most notably that these light quanta, or photons, and electrons sometimes acted like waves and sometimes acted like particles.
The parts of quantum theory that Einstein could never except had to do with randomness. Einstein wanted to see reality as objective. That does not mean that it is just made up of objects. Rather, he wanted the objects (which could include wave-like objects) to be subject to the laws of causality, as he saw them. A number of results of quantum physics collided with Einstein's view of causality, including the Uncertainty Principle [Heisenberg's] and such random events as the decays of nuclear physics (resulting in radioactivity) and in particular the random timing of transitions of electrons when near an atom that result in electromagnetic radiation.
Younger physicists had no problem accepting quantum physics. They seldom saw it as posing a philosophical problem, much less a science one. Einstein's assumption that to have science you need causality, and specifically causality as defined by Isaac Newton, does not hold much weight today among people with PhD's in physics.
Einstein worked until he was on his death bed to find the underlying causes of quantum randomness and probabilities. Long after his death it was postulated, and is now generally believed, that the proton and neutron consist of smaller entities called quarks (more particle like) and gluons (more wave or force-like). If there were some way to measure the positions and velocities of the particles making up the neutrons and protons of an atom, then perhaps it would be possible to predict when a specific atom of a radioactive element would decay. But it is not likely that these decays are the result of the quarks reaching some particular configuration.
Consider dice and solar flares.
Ordinary fair dice, the kind used in casinos and board games, are governed by classical physics. [If you could make them small enough, say a few atoms across, they might start to display true quantum randomness.] They produces random results as long as they are thrown fairly. In theory (and to a surprising degree in practice) you can predict the results if you can sufficiently control how they are thrown and know enough about the surfaces they bounce against before coming up snake eyes, or boxcars, or whatever.
Einstein wanted atomic physics to work like ordinary dice. That would preserve his classical physics version of causality.
Consider solar flares. Scientist know there are patterns to them, but within the envelopes of those patterns they are random. They are mainly classical physics phenomena. They would be predictable if you knew enough about the matter and energy of the sun that gives rise to them. But how would you know that, in advance? You would need some sort of probe that can survive within the sun and send you detailed information about the pre-flare setup.
In fact there are a lot of things we can't know with certainty, for a wide variety of reasons. That does not mean that reality isn't objective. It is because objective reality is complicated. Very to the power of 30 complicated.
For much of my life I tended to favor Einstein's objections to quantum randomness. At some point, however, I realized the problem was more semantic than scientific. In other words, the problem was with how Einstein defined the words objective and causality.
Randomness in quantum physics doe not mean that anything can happen. The randomness in quantum physics is in envelopes. Just as when you roll a pair of dice you may bet any result from 2 to 12, but get 7's more often than other results, in quantum physics you mostly individual get results around a central number, and statistical results from a large set of data are also typically very close to that number.
That is causal enough for me. I accept probability and the statistical nature of results as part of the objective reality of the universe. In fact I have found that seeing the relationship of randomness to cause and effect has been very helpful to me.
I could tell you a story about a preacher who always introduced himself to potential victims with the words "Look around you. Do you believe that this all could be random?" But I have covered enough for one essay.