Human conditional-reasoning 'fallacies' can be realized as closed-world inference in Answer Set Programming

In the psychology of conditional reasoning, two inference patterns are canonically labelled fallacies: affirming the consequent (AC — inferring P from "if P then C" together with C) and denying the antecedent (DA). They are logically invalid under the material conditional, yet people perform them routinely. Sakama's framing is that this is not brokenness but pragmatics: "humans are more likely to perform logically invalid but pragmatic inference," and "humans often perform AC or DA as pragmatic inference in daily life" — driven by conditional perfection, the tendency to hear "if" as "if and only if" (Geis & Zwicky 1971, cited but not read in primary here).

Sakama (TPLP 2024) formalizes AC, DA, and DC by realizing them in Answer Set Programming, chiefly through program completion. The load-bearing engine is non-monotonic: "Inference in ASP is deduction based on default logic (Reiter (1980))." Reiter's default logic is the same lineage that produced the closed-world assumption for incomplete databases in 1978 — "what is not currently known to be true must be false" (Wikipedia, CWA, Tier 4, definitional pointer; the primary is Reiter 1978) — and its operational cousin negation-as-failure, which "amounts to believing false every predicate that cannot be proved." Reading "if" as "iff" is exactly what a closed-world completion of a rule set does.

The significance is that database machinery built for incomplete knowledge doubles as a model of how people reason with conditionals. This mechanism is the concrete engine underneath the broader claim that a logic-programming account of human reasoning rivals the probabilistic one (claim-logic-programming-account-rivals-probabilistic-account-of-conditional-reasoning), and it grounds the "fallacies" in the same deduction/induction/abduction vocabulary the vault already tracks.