Philosophy: The Questions Every Other Field Has to Assume
Physicists assume observation reveals reality; doctors assume suffering is bad. None of those assumptions can be tested by the field relying on them — and someone has to examine them.
Concept
Bayes' Theorem
Epidemiology: Everything Turns on One Number Crossing One
If each case produces more than one further case, an outbreak grows; below one, it fades. That threshold is simple — and almost everything else about the subject is context-dependent.
Simpson's Paradox: True in Every Group, False Overall
A treatment beats its rival for small stones, beats it for large stones, and loses when you combine the patients. Nothing was miscalculated — which is what makes it worth understanding.
The Base Rate Fallacy: Start With How Common It Is
The quiet, bookish stranger sounds like a librarian. There are a hundred times more salespeople — so the shy ones alone outnumber every librarian in the country.
Bayes' Theorem: The 99% Accurate Test That Is Wrong 91% of the Time
A rare disease, a 99% accurate test, a positive result — and roughly a 9% chance you're ill. The gap comes from one number most people leave out entirely.