Failure and Uses of Jaynes' Principle of Transformation Groups

TL;DR

This paper critically examines Jaynes' principle of transformation groups, demonstrating that it cannot uniquely resolve probability ambiguities like Bertrand's paradox and depends on explicit selection procedures.

Contribution

The paper shows that Jaynes' symmetry-based approach does not uniquely solve probability paradoxes and can be replicated by other methods, highlighting its limitations.

Findings

Jaynes' method does not resolve Bertrand's paradox.

Symmetries can be implemented in multiple ways, leading to different solutions.

The principle depends on explicit random selection procedures.

Abstract

Bertand's paradox is a fundamental problem in probability that casts doubt on the applicability of the indifference principle by showing that it may yield contradictory results, depending on the meaning assigned to "randomness". Jaynes claimed that symmetry requirements (the principle of transformation groups) solve the paradox by selecting a unique solution to the problem. I show that this is not the case and that every variant obtained from the principle of indifference can also be obtained from Jaynes' principle of transformation groups. This is because the same symmetries can be mathematically implemented in different ways, depending on the procedure of random selection that one uses. I describe a simple experiment that supports a result from symmetry arguments, but the solution is different from Jaynes'. Jaynes' method is thus best seen as a tool to obtain probability distributions when the principle of indifference is inconvenient, but it cannot resolve ambiguities inherent in the use of that principle and still depends on explicitly defining the selection procedure.