When do we act, how do we act, and how do we justify our decision in a realm of uncertainty and risks? I just read an essay about John Snow and the Cholera epidemic in London 1854. This was yet a time where bacteria were not yet discovered, where a manifold of theories circulated to explain disasters of this kind.
Snow’s observations, his assessment of the situation, his method of interpreting his observations / data made a cause-effect relation transparent that lead the way for an intervention policy stopping the epidemic. With his investigative approach Snow was able to submit all the necessary data that were convincing enough for policy-makers to act.
Snow's map of observations
Source: www.personal.psu.edu