Concepts of reason play a decisive role in the discussion of the different ideas of god in Cicero’s De natura deorum . However, the dialogue uses many different conceptual terms (such as ratio , mens , consilium , intelligentia or cogitatio ) to refer to the achievements and potentials of reason. The variable use of the expressions across the dialogue at first suggests purely rhetorical criteria – variatio delectat – in selecting the terms for reason. However, the investigation presented here into the use of terms reveals that Cicero ascribes to each of his dialogue partners a specific use of terms for reason. As will be shown, the use of terms relates not only to the underlying concepts of reason of the Epicurean, Stoic and Academic schools, but is also closely linked to their ideas about god.