The study ofthe effects ofcontent has been the prime concern ofresearchers on reasoning for 20 years or more. Indeed, a quick glance at the chapter headings for this volume will confirm that observation: several chapters are devoted to various aspects of the issue, and this is one of them. Our topic is deontic reasoning, which actually has its own special logical form as well as content. We shall begin by tracing how this topic emerged out of the general background of research on content effects, though it is not a topic which should only be of interest to a narrow range of reasoning researchers. It is one offundamental importance for understanding human thought and behaviour.