This monograph will likely become a classic. It provides critical insights into identifying which threads to pull in the "web of causation" (see chapter IX) to discern the impact of adverse early life experiences, and it provides guidance regarding how to identify patterns of behavior that are likely to reflect the impact of such experiences. Not everyone will agree with all the decisions and, hence, all the conclusions made by these authors. Indeed, I have concerns about some of them as I discuss below. However, the authors provide access to their deliberative process in such a rich way that the reader can follow not only what they did but also the many considerations behind their choices, their own equivocating and reversals as more data accumulated, and the broad theoretical concerns that guided their decisions. Because "natural experiments" always confront researchers with difficult choices among never perfect options, their decision to provide a detailed discussion of their deliberative process, in addition to the richness of their data and the importance of their topic, is what makes this a likely classic in the field.