Agreed. I tend to cringe at essentialism, which can be applied to any concept. At the same time, I cringe at its opposite. If the idea of an unknown entity is n

Agreed. I tend to cringe at essentialism, which can be applied to any concept. At the same time, I cringe at its opposite. If the idea of an unknown entity is not entertained, held in suspension as it were, in one's mind, I think that theory suffers. As you point out, "practically predictable" is where I would stand. Or "random enough". When I was little, in France, I was explained that the Meter was defined according to the length of a platinum alloy standard sitting in an institute in Paris... Bottom line: Randomness, is a philosophical concept, predictability is a scientific concept, asymptotic to 0, another needed absolute...