This little book is the result of a relapse. I thought I had long since been cured of the (juvenile) affliction of literary theory, but clearly I was not permanently immunized. Many years ago, when I too was a victim of the widespread epidemic, I wrote an essay pursuing those interests. Once the fever had abated I followed a different course. I occupied myself with interpreting poetic texts, then prose texts, and I composed a history of Latin literature then I devoted myself to textual criticism and also prepared critical editions. In short, I practiced the usual trade-skills of a classical philologist. However, those earlier experiments with literary theory helped me to refine a method of textual analysis (a pursuit which in our profession has been honored by a long tradition of scholarship). Other scholars, not only in Italy but in Great Britain and the United States, have since accompanied me on that path, often explicitly referring to the ideas I articulated, at times with additions and developments.