When a system fails to meet its specification, it can be difficult to find the source of the error and determine how to fix it. In this paper, we introduce error reporting logic (ERL), an algorithm and tool that produces succinct explanations for why a target system violates a specification expressed in first order predicate logic. ERL analyzes the specification to determine which parts contributed to the failure, and it displays an error message specific to those parts. Additionally, ERL uses a heuristic to determine which object in the target system is responsible for the error. Results from a small user study suggest that the combination of a more focused error message and a responsible object for the error helps users to find the failure in the system more effectively. The study also yielded insights into how the users find and fix errors that may guide future research.