The authors of this article write in their abstract: "Are there fundamentally random processes in nature? Theoretical predictions, confirmed experimentally, suc

The authors of this article write in their abstract: "Are there fundamentally random processes in nature? Theoretical predictions, confirmed experimentally, such as the violation of Bell inequalities, point to an affirmative answer. However, these results are based on the assumption that measurement settings can be chosen freely at random, ..." [1] From its inception, quantum mechanics has used the language of probability to make calculations (this is the "Born rule" that another poster refers to), but this does not mean that the universe behaves randomly. Perhaps, as you suggest, this language of probability conceals human ignorance. To test this, we define a physical property called "realism" that says, roughly, "every experiment has a result that was knowable beforehand". If realism does not hold, then the results of some physical experiments are somehow randomly determined at the moment that the experiments are performed. A set of famous experiments (the "Bell's inequality experiments" [2]) have shown that, with certain assumptions, "local realism" does not hold, i.e. locality and realism do not simultaneously hold. Locality is the idea that it is possible to perform two experiments in sufficiently separated regions of the universe so that they cannot possibly influence each other. If general relativity were a complete theory, for instance, then we would have locality (because no signal could travel faster than light). Almost all non-specialist physicists (physicists who use quantum mechanics but do not spend time trying to assess its foundations) accept locality and accept that the Bell experiments rule-out local realism. This means that they give-up realism, and these physicists say that nature is "fundamentally random". Some physicists try to give-up locality instead, and you will hear them talk about "non-local hidden variable theories". Other physicists, such as the authors of the linked-to "Nature" article, play carefully with the assumptions behind using the Bell experiments to rule-out local realism. For instance, they point-out the assumption that "measurement settings can be chosen freely at random". If this assumption does not hold, neither does Bell's proof. All-in-all you are in excellent company if you say that physical processes are fundamentally random, but there are many specialist physicists who grapple with this question in their daily work. [1] http://arxiv.org/abs/1105.3195 http://arxiv.org/abs/1105.3195 [2] http://en.wikipedia.org/wiki/Bell_test_experiments http://en.wikipedia.org/wiki/Bell_test_experiments