Why did the Principle of Double Effect Appear in the West?

Abstract

Writers within the natural law tradition share at least two basic assumptions: (1) there is a common humanity (or human nature) which (2) makes possible universally valid moral principles. Among the formulated norms of this tradition is the principle of double effect (hereafter PDE). The following essay responds to three questions about this principle: (1) As it emerged historically, what ties did PDE have to a particular religious tradition? (2) Can it have had such historical roots and still be reflective of a “common humanity”? (3) If PDE has such parochial roots, how can it be part of what is said to be a set of universally valid moral principles? These questions provide a specific instance of the more general question that bedevils most discussions of the natural law: If there is such a common or universal moral law, why is there so much diversity in moral beliefs and practices? Perhaps, if PDE is shown to be defensible independently of the assumptions of a particular religious tradition, the same analysis may be useful in answering the more general question. What follows is, first, a speculative genealogy offering a plausible reconstruction of the reasons for the emergence of PDE in Christian moral theology. Then the question is how this historically emergent principle may reflect common moral experiences and insights beyond those of any particular religious tradition. Next is the response to the question of how “locally” formulated principles may have a universal validity. This response is followed by remarks that qualify the usual way of talking about the natural law in terms of “principles.” These qualifying remarks address the broad question of reconciling talk of a universal moral law with the fact of diversity in moral beliefs and practices.