Tail event: Difference between revisions

When we roll dice to ''determine'' an outcome we do not build a statistical model that predicts a ⅙ probability: we build the dice to yield the that outcome. A die is part of what [[Nancy Cartwright]] would call a “[[nomological machine]]”:<ref>This is a ''terrible'', typically ''academic'' label. No doubt it is etymologically accurate, but it is forbidding to a lay reader. Academics , like lawyers, tend to do this while they train and occupy the junior rungs as a self-credentialising device. By the time they sit on the higher rungs, they don’t know any different way of writing.Cartwright is a brilliant thinker, but her writing is dense and hyper-academic. </ref> a carefully designed, constrained, hermetically-sealed simple system, designed to generate a specific theoretical outcome. If over time our dice don’t yield a ⅙ outcome we don't throw out the statistical model: we throw out the ''dice''.

The “map” and territory ” are transposed: the dice are the map, the theoretical ⅙ probability is the territory. The map is, as far as engineering permits, ''identical'' to the territory. Now each of us has a difference engine in our pocket, we don’t even need physical dice: we could generate the same outcome, with a random number generating app.

The machined dice and the flat, constrained surface con which they fall are not meant to represent our actual reality. They are aspiring to the desired statistical model. They seek to emulate an idealised platonic form. A “loaded” die is a ''flawed'' nomological machine. So is a surface like sand which allows a die to rest on its corner. If you get bad results with a nomological machine you don't chuck out the theory: you chuck out the equipment.

Likewise, if, inside your nomological machine there is a mischievous imp who catches and places the die as it sees fit, the conditions for your probabilistic calculation do not prevail. There must be no interfering causal agency.  

“Nomological machines” are highly constrained, artificial environments. If all their conditions are not satisfied, we can expect the world to behave differently without validating the machine. This is how, as [[Nancy Cartwright]] put it “the laws of physics lie”.

In any case, these are the circumstances in which the rules of probability prevail. Should the universe “misbehave” then the conditions required for the nomological machine cannot be present.

Boy did I get sidetracked.  

Normal distributions standard deviations, and confident probabilities require a complete nomological machine where all potential events are known, are independent, and there is no intervening agency that can upset the observed behaviour of the system. If you have all that all risks can be calculated and probabilities assigned.