Note on the Principle of Detailed Balancing

The following formulation is suggested for this principle: "No system in thermal equilibrium in an environment at constant temperature spontaneously and of itself arrives in such a condition that any of the processes taking place in the system by which energy may be extracted, run in a preferred direction, without a compensating reverse process." It is shown that, granted the physical reality of the process, the principle follows from the second law of thermodynamics.