  The Transactional Interpretation offers a solution to the measurement problem
by identifying specific physical conditions precipitating the non-unitary
`measurement transition' of von Neumann. Specifically, the transition occurs as
a result of absorber response (a process lacking in the standard approach to
the theory). The purpose of this Letter is to make clear that, despite recent
claims to the contrary, the concepts of `absorber' and `absorber response,' as
well as the process of absorption, are physically and quantitatively
well-defined in the transactional picture. In addition, the Born Rule is
explicitly derived for radiative processes.
