  Recent advances in nonequilibrium statistical mechanics shed new light on the
ratchet effect. The ratchet motion can thus be understood in terms of symmetry
(breaking) considerations. We introduce an additional symmetry operation
besides time-reversal, that effectively reverses the nonequilibrium driving.
That operation of field-reversal combined with time-reversal decomposes the
nonequilibrium action so to clarify under what circumstances the ratchet
current is a second order effect around equilibrium, what is the direction of
the ratchet current and what are possibly the symmetries in its fluctuations.
