In this paper I study the expression χύσις τῆς κακίας, frequently used by Origen of Alexandria. The identification of its variants in Origen gives some criteria to identify its occurrences in pre-origenian literature. Three possible sources are examined: the pagan literature, the Scripture and Philo of Alexandria; the latter is most likely the model for Origen. Before studying the use of χύσις τῆς κακίας and its variants in Origen, I discuss the frequency of these expressions in his works. Curiously enough, Origen uses them far more often in the 'Against Celsus' than in his other works. The most likely explanation is that the topics discussed in the apology led him to have recourse to these expressions. A survey of the multiple meanings of χύσις τῆς κακίας and its variants in all his works but the 'Against Celsus', then in the latter, confirms this hypothesis. Finally, I stress the originality of Origen. Although he probably found χύσις τῆς κακίας and its variants in Philo, Origen uses them in a different way: to demonstrate the necessity and the significance of Christ’s actions. An addendum presents some possible traces of χύσις τῆς κακίας and its variants in the Latin translations of Origen’s works.