There is a lot of talk these days about thinking historically. Policy makers use the term. So do teachers, curriculum writers, test makers, and administrators. And above all researchers use it--a lot. A number of articles have been published in this very column concerning the topic, many by those who do history-education research. Some might argue that the term "thinking historically" has become nothing more than educational jargon, that educators use it as a metaphor for a significantly broad range of activities that occur in any given social studies classroom. Others might say that the term means different things to different people. As a result, it can be difficult to know what it means to teach it. The author attempts to address the question posed in the title, and clarify what is meant by historical thinking and therefore shed some light on how it could be more successfully taught. (Contains 17 endnotes.)