Why abduction matters
Population-level causal effects answer "on average, what would happen under intervention?" — but individual-level counterfactuals require something more: the specific, unobserved background factors that made this patient's outcome what it was. Abduction recovers those factors from what was actually observed, anchoring each U node to the value consistent with the facts of the case.
Without abduction, a counterfactual query uses population-average noise — which may be badly wrong for any particular individual. With it, you hold the patient's background fixed and ask what would have happened under a different prescription: the same person, different treatment. This is Rung 3 Step 1 of Pearl's three-step counterfactual procedure — the formal engine behind personalised medicine and individual liability assessment.