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Jayson_Virissimo comments on What is Bayesianism? - Less Wrong

81 Post author: Kaj_Sotala 26 February 2010 07:43AM

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Comment author: Jayson_Virissimo 27 February 2010 01:40:25AM *  4 points [-]

Bayesianism is more than just subjective probability; it is a complete decision theory.

A decent summary is provided by Sven Ove Hansson:

  1. The Bayesian subject has a coherent set of probabilistic beliefs.
  2. The Bayesian subject has a complete set of probabilistic beliefs.
  3. When exposed to new evidence, the Bayesian subject changes his (her) beliefs in accordance with his (her) conditional probabilities.
  4. Finally, Bayesianism states that the rational agent chooses the option with the highest expected utility.

The book this quote is taken from can be downloaded for free here.

Comment author: wnoise 27 February 2010 09:34:16AM 2 points [-]

What Bayescraft covers is a matter of tendentious definitions. I personally do not consider decision theory a necessary part of it, though it is certainly part of we're trying to capture at LessWrong.

Comment author: Douglas_Knight 28 February 2010 01:44:57AM 4 points [-]

I agree. The line between belief and decision is the line between 3 and 4 in that list and it is such a clean line that the von Neumann-Morgenstern axioms can be (and usually are) presented about a frequentist world.