The long and winding road to causality

Epidemiologists face two fundamental and interrelated problems when judging causality: knowledge is fallible, and studies are imperfect. In medicine, this will always leave a degree of uncertainty in scientific judgements. From an epistemological point of view, even randomized trials cannot be regarded as the ultimate proof to establish a causal relation. Given this inherent uncertainty it is no surprise that much attention has been drawn to the question how we can move from an association to a valid judgement of causation. It was exactly this question that urged Austin Bradford Hill more than 50 years ago to his well-known and still worth-reading paper, in which his nine viewpoints (often referred to as Hill’s criteria) to judge causality were described.