1. Some large percentage, possibly more than half, of what a doctor does is diagnosis and prognosis. This is all pure probability. Failure to understand the dif

1. Some large percentage, possibly more than half, of what a doctor does is diagnosis and prognosis. This is all pure probability. Failure to understand the difference between Prob(A|B) and Prob(B|A) has nontrivial consequences. 2. Frontier areas of medicine -- oncology, psychiatry -- deal increasingly with uncommon situations that not necessarily happen with enough frequency for a doctor to develop a doctorly intuition. There are some great resources -- meta-analyses, for example -- out there, but if we keep cutting slack to practitioners and let them follow the word of "thought leaders", medicine becomes the prey of ideological waves and conceptual fashions.