Ph.D. dissertations , or theses, come in many flavors.
At one end of the scale , they have the form of an introduction with chapters that follow each other in a logical, coherent way. Each of the chapters answers a research question, and these research questions are subquestions of one main research question.
At the other end of the scale, a dissertation or thesis consists of a number of previously published articles, with an introduction and conclusions or an epilogue at the end. These chapters loosely cover the same subject, but it is difficult to find a logical structure, or to define a main research question based on the individual research questions. This entry contains advice for an introduction for the latter type of dissertation.
I finished my Ph.D. dissertation, Design for Change, recently; it was definitely an example of the latter type. It contains eight chapters based on previously published articles, written over a long period of time, touching a broad set of subjects. Here, I describe how I tackled the problem of binding those chapters together in the introduction of the dissertation (I will use the word thesis from now on, because it is shorter).