Search engines find facts. An Explainer Engine finds explanations. Once a system is described by a set of Cause and Effect relations, one can then find explanations for observed behavior or how to obtain desired behavior by solving these Cause and Effect relations. Up to now, it has been computationally wicked to solve cause and effect relations of any practical size. We have made a breakthrough by developing a computationally efficient algorithm that would make it quite practical to have Explainer Engines. Explainer Engines could be used to diagnose medical problems or problems with most any type of machine. Cause and effect is a basic method of reasoning and is the foundation of the scientific method.