On \textit{prima facie} obligations and nonmonotonicity (Q2454878)

This brief paper challenges the claim, as expressed by \textit{D. Nute} and \textit{X. Yu} [``Introduction'', in: D. Nute (ed.), Defeasible deontic logic. Dordrecht: Kluwer Academic Publishers. Synth. Libr. 263, 1--16 (1997; Zbl 0913.03008)], that the notion of \textit{prima facie} obligation ``cries out for a defeasible or nonmonotonic analysis''. The argument is cogent, though more philosophical than formal, especially as the notion of \textit{prima facie} obligation is understood in terms of \textit{pro tanto} reasons for acting. The paper does not explore whether theories of nonmonotonic reasoning might have other useful applications in deontic logic.