 Philosophers have, for quite some time, been interested in defeasible obligations, which give rise to defeasible inferences about what we are, all things considered, obliged to do. David Ross, in 1930, discussed the phenomena of prima facie obligations (Ross 1930, 1939). The existence of a prima facie obligation gives one good, but defeasible grounds, for believing that one ought to fulfill that obligation. When formal deontic logic was developed by Chisholm and others in the 1960s (Chisholm 1963), the use of classical logic gave rise to certain paradoxes, such as Chisholm’s paradox of contrary-to-duty imperatives. These paradoxes can be resolved by recognizing that the inference from imperative to actual duty is a defeasible one (Asher and Bonevac 1996; Nute 1997). 