On the Statistical Viewpoint Concerning the 2nd Law of Thermodynamics a Reminder on the Ehrenfests' Urn Model

In statistical thermodynamics the 2nd law is properly spelled out in terms of conditioned probabilities. As such it makes the statement, that `entropy increases with time' without preferring a time direction. In this paper I try to explain this statement--which is well known since the time of the Ehrenfests--in some detail within a systematic Bayesian approach.Comment: 18 pages, no figures. This paper is my contribution to the book "From Quantum to Classical - Essays in Honour of H.-Dieter Zeh", edited by Claus Kiefer, that appeared in 2022 as volume 204 in the series Fundamental Theories of Physics at Springer Verlag. It is an extended version of the previous version (V1) containing an additional introduction and more reference