Objective Bayesianism and Geometry

We suggest in this paper that the concepts of utility, prior probability and entropy are not independent but must be related through the following formula: “The expected utility of a Theory is an increasing funetion of its entropy.” It follows that associated to each regular class of theories (i.e. parametric statistical model) there is a unique one parameter family of densities able to act as prior distributions. These entropic priors form the exponential family generated by the invariant measure in the class, that has the entropy of each theory as sufficient statistic.