 If memory is a capacity for tracking our own past experiences and witnessings then a necessary condition for Penelope remembering giving a lecture is that it occurred in the past. Contrariwise, that Penelope now remembers the lecture is sufficient for inferring that it was given in the past. In a well-known attempt to use the terminology of necessary and sufficient conditions to illuminate what it is for one thing to be cause of another thing, J. L. Mackie proposes that causes are at a minimum INUS conditions, that is, “Insufficient but Necessary parts of a condition which is itself Unnecessary but Sufficient” for their effects (Mackie 1965). A schema like Mackie’s became the foundation for the “sufficient cause model” of disease in epidemiology (see Rothman 1976) and continues to have influence on medical thinking about disease causation, as well as on definitions of causation in psychology and law (VanderWeele 2017).