As media reports have made widely known, in November 2009, the ethics committee of St. Joseph's Hospital in Phoenix, Arizona, permitted the abortion of an eleven-week-old fetus in order to save the life of its mother. This woman was suffering from acute pulmonary hypertension, which her doctors judged would prove fatal for both her and her previable child. The ethics committee believed abortion to be permitted in this case under the so-called principle of double effect, but Thomas J. Olmsted, the bishop of Phoenix, disagreed with the committee and pronounced its chair, Sister Margaret McBride, excommunicated latae sententiae, "by the very commission of the act." In this article, I take the much discussed Phoenix case as an occasion to subject the principle of double effect to another round of philosophical scrutiny. In particular, I examine the third condition of the principle in its textbook formulation, namely, that the evil effect in question may not be the means to the good effect. My argument, in brief, is that the textbook formulation of the principle does not withstand philosophical scrutiny. Nevertheless, in the end, I do not claim that we should then "do away" with the principle altogether. Instead, we do well to understand it within the context of casuistry, the tradition of moral reasoning from which it issued.