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Counterfactuals in Logic Programming with Applications to Agent Morality

Computational morality is an interdisciplinary field emerging from the need of imbuing autonomous agents with the capacity for moral decision-making. This paper supplies a computational model, via Logic Programming (LP), of counterfactual reasoning of autonomous agents with application to morality. Counterfactuals are conjectures about what would have happened, had an alternative event occurred. The first contribution of the paper is showing how counterfactual reasoning is modeled using LP, benefitting from LP abduction and updating. The approach is inspired by Pearl’s structural causal model of counterfactuals, where causal direction and conditional reasoning are captured by inferential arrows of rules in LP. Herein, LP abduction hypothesizes background conditions from given evidences or observations, whereas LP updates frame these background conditions as a counterfactual’s context, and then imposes causal interventions on the program through defeasible LP rules. In the second contribution, counterfactuals are applied to agent morality, resorting to this LP-based approach. We demonstrate its potential for specifying and querying moral issues, by examining viewpoints on moral permissibility via classic moral principles and examples taken from the literature. Application results were validated on a prototype implementing the approach on top of an integrated LP abduction and updating system supporting tabling.