A recent article in the March 2009 edition of Clinical Ethics stated that, ‘In the Summa Theologica, Thomas Aquinas discusses how murder may be justified in self defence’, provided that killing is not intended. This statement is open to challenge on historical and semantic grounds, with respect to the writings of the 13th Century Roman Catholic philosopher Thomas Aquinas (1225–1274). A better appreciation of Aquinas' writings on this topic could inform the debate relating to medical end-of-life decisions. The normatively loaded (...) word ‘murder’ is not applicable to Aquinas' conclusion on unintended homicide, nor is it applicable to unintended homicide in current law, which is by definition not murder. (shrink)