Greg Loeben, Michelle A Chui
Extract
It seems clear from these observations that Card (2007) uses the zero probability argument as a bit of a straw man. The conscientious objector does not rely on such a simplistic claim. In fact, conscientious objection can and should be evaluated in light of a variety of components, rather than the mere possibility that one’s actions will contribute to an unethical result. Specifically, conscientious objection appears to be made more plausible by a variety of factors, including the likelihood, intentionality, causal directness, degree of consensus, and not least, the severity of the unethical action.
Loeben G, Chui MA. Conscientious Objection: Does the Zero-Probability Argument Work? (Conscientious Objection and Emergency Contraception). Am J Bioeth. 2007 Jun;7(6):28-30.