What is it about the process of diagnosis that eludes critical evaluation? Clinicians make millions of diagnoses every day, and making the right one is central to effective treatment and accurate prognosis. Great diagnosticians tend to be forgiven their other human failings, if the television portrayal of rude but brilliant Dr Gregory House is anything to go by (BMJ 2005;330:1090, doi:10.1136/bmj.330.7499.1090), which suggests that much of the prestige of medicine is bound up with the ability to diagnose. Yet we know surprisingly little about the thought processes behind successful diagnosis.

A new series launched this week aims to encourage clearer …