Historians use cookbooks as primary source documents in much the same way they use any written record of the past. A primary source is a text written by someone in the past, rather than a secondary source which is commentary by a historian upon the primary sources. As with any document, the historian must attempt to answer five basic questions of provenance and purpose if possible. Who wrote the cookbook? What was the intended audience? Where was it produced and when? Why was it written? There are ways the historian can read between the lines of the recipes, so to speak to answer questions that are not directly related to cooking or material culture but may deal with gender roles, issues of class, ethnicity and race. Even topics such as politics, religion and world view are revealed in the commentary found in cookbooks and sometimes embedded in what appears to be a simple recipe. The most valuable of cookbooks and related culinary texts also reveal what we might call complete food ideologies.