Which of Hill's viewpoints is considered the most essential?

The most essential viewpoint among Hill's criteria for causation is temporality. This concept emphasizes that for one event to be considered a cause of another, the cause must precede the effect in time. Establishing a clear temporal relationship is crucial because it helps to eliminate doubt about whether the exposure or the risk factor occurred before the outcome. In epidemiology and causal inference, demonstrating that the cause came before the effect aids in making stronger, more valid claims about causation rather than mere correlation.

In studies of health and disease, if the exposure is shown to take place prior to the onset of the disease, it allows researchers to better understand the sequence of events, supporting the hypothesis that the exposure contributed to the outcome. By establishing temporality, researchers can provide stronger evidence for other criteria like strength, plausibility, and coherence, but without it, causality becomes much harder to justify.