  The notion of a physical collapse of the wave function is embodied in
dynamical collapse models. These involve a modification of the unitary
evolution of the wave function such as to give a dynamical account of collapse.
The resulting dynamics is at first sight time asymmetric for the simple reason
that the wave function depends on those collapse events in the past but not
those in the future. Here we show that dynamical wave function collapse models
admit a general description that has no inbuilt direction of time. Given some
simple constraints, we show that there exist empirically equivalent pictures of
collapsing wave functions in both time directions, each satisfying the same
dynamical rules. A preferred direction is singled out only by the asymmetric
initial and final time constraints on the state of the Universe.
