Are Causes Ever Too Strong? Downward Monotonicity in the Causal Domain

Is the truth of a causal claim always preserved by strengthening the cause? For instance, does “Alice flicking the switch caused the light to turn on” entail “Alice flicking the switch and it raining in New Zealand caused the light to turn on”? We argue for this entailment, proposing that causal claims are downward monotone in their cause: if C+ entails C then (C caused E) entails (C+ caused E). In other words, causes are never too strong. We argue for this by presenting examples of causal claims that are assertable even though the cause is stronger than required for the claim to be true (Sect. 2). These data challenge accounts (the most prominent of which is Halpern, Actual Causality 2016) that predict such sentences to be false. Instead, we trace differences in their acceptability to their scalar implicatures (Sect. 3). Finally, we show that Halpern’s semantics of causal claims can be easily adapted to account for the data we consider; namely, by dropping his ‘minimality’ condition (Sect. 4).