Institutio Oratoria

The act itself again sometimes involves a single question, as, for example,

whether a man is dead, and sometimes two, as, for instance, whether he died of poison or of some internal disease. Another form of conjecture is concerned with the act alone, it being admitted that if the act was really committed, there can be no doubt as to its author. A third form is concerned solely with the author, the act being admitted and the dispute turning on the question as to who committed it. This third form is complex.