In this chapter, I examine how voluntas helps the young lawyer Cicero craft arguments and structure relationships with Roman clients, witnesses, and juries. In the De inventione and forensic speeches, we see his struggle to reconcile tradition with new intellectual tools. As he seeks to bring ratio more fully into Roman legal culture, voluntas plays a plural and ambiguous role. It is an instrument of rational inquiry, as in the competing schemata of criminal responsibility he examines in the De inventione. As it has always been in Roman law, voluntas is the desire of a legally relevant individual, emanating from and attributable to him alone – the marker of his agency and responsibility. So, too, however, is it used to signify the collective goodwill of an audience, which Cicero makes clear is the expert orator’s plaything. The “goodwill” sense of voluntas adds greatly to its durability in moral philosophy. While a sententia or iudicium pertain to a specific question, voluntas marks an ongoing choice or disposition, such as the will of a legislator, to be conserved. Cicero’s objectives for the law go largely unachieved in his time, but they expand Rome’s intellectual field of vision.