Downward. EOCS must reflect the fact that in a large number of cases, accepted scientific theories are the starting point for the construction of computer simulation models and play an important role in the justification of inferences from simulation results to conclusions about real-world target systems. The word “downward” was meant to signal the fact that, unlike most scientific inferences that have traditionally interested philosophers, which move up from observation instances to theories, here we have inferences that are drawn (in part) from high theory, down to particular features of phenomena.