De libero arbitrio diatribe sive collatio

De libero arbitrio diatribe sive collatio (literally Of free will: Discourses or Comparisons) is the Latin title of a polemical work written by Desiderius Erasmus of Rotterdam in 1524. It is commonly called The Freedom of the Will or On Free Will in English. De libero arbitrio diatribe sive collatio was written expressly to refute a specific teaching of Martin Luther, on the question of free will. Luther had become increasingly aggressive in his attacks on the Roman Catholic Church to well beyond irenical Erasmus' reformist agenda. Luther published in 1520 his Assertio omnium articulorum (itself a response to Pope Leo X's bull Exsurge domine that threatened Luther with excommunication) which included the statement God effects the evil deeds of the impious as part of the Wycliffian claim that everything happens by pure necessity, so denying free will. Erasmus decided this was a subject of core disagreement, and strategized for several years with friends and correspondents on how to respond with proper moderation without making the situation worse for all. Erasmus' eventual strategy had three prongs: first, a dialogue Inquisitio de fide to turn down the general heat and danger, which asked the question of whether Lutherans were heretics and, because they accepted the Creed, proposed that Lutherans were not; second, a small book On Free Will addressed as much to issues of limits of authority, discourse, biblical interpretation, as to free will; third, a small book De immensa misericordia dei (On the Immense Mercy of God), written ostensibly as a model sermon, published the same day as On Free Will and not mentioning Luther; it set up that God was not arbitrary, against the claims of predestination. Synergism is the idea that adult salvation or justification involves some sort of co-operation (noting that the co- does not connote equality of the parties, God's grace always being in some way prior.) This is the view that Erasmus promotes in On Free Will. Monergism is the idea that God brings about an individual's salvation or justification regardless of their co-operation.