PERSONAL RISK CONCEPTS · 6 MIN READ

Causation Doctrines and Multiple-Cause Losses

When one peril causes a loss, coverage is easy. The hard questions come when covered and excluded perils combine, and three distinct frameworks decide the outcome. The default concurrent-causation rule, articulated in the Restatement (Third) of Property: Liability Insurance Section 49, favors the insured: when a covered cause and an excluded cause both contribute to a single indivisible loss, the loss is covered — unless the policy clearly says otherwise. Insurers say otherwise through anti-concurrent causation (ACC) language, which excludes loss caused directly or indirectly by the excluded peril regardless of any other cause contributing concurrently or in any sequence. Enforceable ACC wording flips the default: the excluded peril's participation defeats coverage for the combined loss. A minority of jurisdictions apply the efficient proximate cause doctrine instead. It asks which cause set the chain of events in motion and treats that predominant, initiating cause as controlling: if the efficient proximate cause is covered, the whole loss is covered even though an excluded peril contributed downstream. Some of these states hold, as a matter of public policy, that ACC clauses cannot override efficient proximate cause analysis. Distinguish both doctrines from apportionment, which applies when the damage is divisible: if hail damaged some shingles ($8,000) and pre-existing wear independently damaged others ($2,000), the insurer simply pays the covered portion and declines the excluded portion — ACC language is irrelevant because the wear damage was never caused by hail at all. Round out the causation toolkit with the liability-side concepts. An intervening cause is a later event in the causal chain that does not break liability; a superseding cause is so unforeseeable that it cuts off the original actor's liability. Related policy features reinforce the covered-cause analysis: direct physical loss is the trigger for property coverage while indirect consequential loss needs its own coverage part, defective-construction exclusions strip coverage from the faulty work itself (often while covering ensuing losses), and vacancy provisions in homeowners forms restrict certain perils when the dwelling has been left vacant.