  How is it that entropy derivatives almost in their own are characterizing the
state of a system close to equilibrium, and what happens further away from it?
We explain within the framework of Markov jump processes why fluctuation theory
can be based on considerations involving entropy production alone when
perturbing around the detailed balance condition. Variational principles such
as that of minimum entropy production are understood in that way. Yet, further
away from equilibrium, dynamical fluctuations reveal a structure where the
time-symmetric sector crucially enters. The fluctuations of densities and
currents get coupled and a time-symmetric notion of dynamical activity becomes
the counterpart and equal player to the entropy production. The results are
summarized in an extended Onsager-Machlup Lagrangian, which in its quadratic
approximation is expected to be quite general in governing the small
fluctuations of nonequilibrium systems whose macroscopic behavior can be
written in terms of a Master equation autonomously describing the
time-dependence of densities and currents.
