In his textbook of moral theology, Henry Davis, an English Jesuit theologian, wrote that of all the principles of moral theology, the principle of material cooperation is the most difficult to apply. The principle is used to analyze the contribution one makes or the assistance one gives to the wrong
“Students who understood very little of his lectures told me that they attended because they ‘felt better’ about themselves in his presence. ‘This is a professor to whom I can confess,’ one said.”