Abstract

The essay begins with an explanation of St. Alphonsus Liguori’s understanding of the distinction between formal and material cooperation, identifying also some problems inherent in that understanding. The essay goes on to expound related ideas in the writings of St. Thomas Aquinas, ideas that are applicable to cases not easily analyzable by means of the distinction between formal and material cooperation. The essay then applies these ideas to two contemporary issues: the use of vaccines connected in some way with abortions and the objection by the Little Sisters of the Poor to the contraceptive mandate issued by the US Department of Health and Human Services.