Human conditional reasoning is defeasible: people withdraw
logically valid conclusions if they are aware of situations (i.e.,
exceptions) that prevent the consequent of the rule to happen
although the antecedent is given. In this paper we investigate
defeasible reasoning with quantified rules. In two experiments
we rephrased conditionals from the literature (Experiment 1)
and rules from penal code (Experiment 2) as either universal
or existential rules and embedded them into Modus Ponens
and Modus Tollens inference problems. We show that defeasible
reasoning also exists for quantified rules. However, the
kind of quantifier (universal vs. existential) did not affect inferences.
This last finding conflicts with theories highlighting
the importance of logic in human reasoning.