[epidemiology]

In introductory epidemiology courses you'll usually get the Bradford Hill criteria in the first week or two, which gives a good foundation of determining public health causality. After digging deeper, the entire field of causal inference is revealed.

A healthy respect for the difficulties of determining causality is beneficial. Irrational skepticism ignoring the evidence of strong observational research simply replaces it with... what exactly? That's how we ended up with an 71 year old anti-vaccine conspiracist as the health secretary.