[Learning concepts of diagnosis in family medicine: the "mark robinson sign" - the traces that should not be there].

We review the mechanisms of the mental operation to identify the disease in family medicine, using five cases where the diagnosis process began in "the trace that should not be there" or "Robinson sign" as happened to Robinson Crusoe when he saw a human footprint on the beach of the "desert island". How could it be there?; It was a mystery, and based on metaphors, we framed the mechanism of "the trace that should not be there" mainly in the first phase of clinical or intuitive reasoning, but this intuition of the doctor should be accompanied by the diagnostic process, like the "basso continuo" of Baroque music, allowing improvisation and personal style, and in this way, eventually observing the footprint "that should not have been there" that may arise in the analytical, as well as in the verification phase of the assumptions made.