 Both causal and unification accounts, as typically conceived, assume that theories are in place and that the models of those theories play some role in explanation. In causal accounts, causal processes are key components of the models. In unification accounts, laws might be the ultimate explanatory factors, but we often connect laws with physical systems via models. To be explanatory, however, such accounts must make the faithful model assumption; namely, that our models (and their state spaces) are faithful in what they say about actual systems. 