We observe an event and then we seek to explain its cause. This is commonplace. A person contracts lung cancer; what caused it? There was a traffic accident; what caused it? A school’s public examination results are outstandingly high; why? The staff turnover in a school suddenly escalates; why? The researcher is looking for the causes of effects. The determination of causes from effects is rather like forensic investigations in police detection. Detectives work forensically and meticulously, looking for motives, the chain of events, the details of the events, working on clues and hypotheses; so it is with piecing together causes from an examination of the effects. It is provisional, probabilistic, uncertain, and requires scrupulous attention to detail: high ‘granularity’.