In “The Contralife Argument and the Principle of Double Effect” (NCBQ, Spring 2011), Lawrence Masek tries to use the principle of double effect to show that natural family planning (NFP) is morally justified. This essay presents a summary explanation of the principle of double effect. It demonstrates that Masek wrongly applies the principle of double effect to NFP. It presents the teaching of the 1968 papal encyclical Humanae vitae with regard to NFP, and contends that to apply the principle of (...) double effect to the case of NFP is not only incorrect but also contrary to teaching of Humanae vitae. Because Masek implies that NFP involves the (justified) permission of evil, his article also counteracts the efforts of the Catholic Church to promote the practice of NFP. National Catholic Bioethics Quarterly 11.4 (Winter 2011): 661–667. (shrink)