Online research in philosophy

Irreversibility, it is claimed, is a much broader concept than is entropy increase, as is shown by the occurrence of certain processes which are irreversible without seeming to involve any intrinsic entropy change. These processes include the spreading outwards into space of particles, or of radiation, and they also include certain biological and mental phenomena. For instance, the irreversible and treelike branching which is characteristic of natural evolution is not entropic when it is considered in itself—i.e. in abstraction from accompanying (...) biochemical and physiological activity. What appears to be the common feature of all forms of irreversibility is the fanning out of trajectories, new entities or new states, in the temporal direction towards the future. (shrink)

It is only when mixing two or more pure substances along a reversible path that the entropy of the mixing can be made physically manifest. It is not, in this case, a mere mathematical artifact. This mixing requires a process of successive stages. In any finite number of stages, the external manifestation of the entropy change, as a definite and measurable quantity of heat, isa fully continuous function of the relevant variables. It is only at an infinite and unattainable limit (...) thata non-uniform convergence occurs. And this occurs when considered in terms of the number of stages together with a distinguishability parameter appropriate to the particular device which is used to achieve reversibility. These considerations, which are of technological interest to chemical engineers, resolve a paradox derived in chemical theory called Gibbs'' Paradox. (shrink)

An important contribution to the foundations of probability theory, statistics and statistical physics has been made by E. T. Jaynes. The recent publication of his collected works provides an appropriate opportunity to attempt an assessment of this contribution. * Review of E. T. JAYNES (1983): Papers on Probability, Statistics and Statistical Physics. Edited by R. D. Rosenkrantz. D. Reidel Publishing Company. US $49.50. Pp. xxiv + 434. We are grateful to Harvey Brown, Kenneth Denbigh, Udi Makov and Oliver (...) Penrose for their valuable criticisms of this paper. (shrink)