De libero arbitrio diatribe sive collatio

On the Freedom of the Will
AuthorErasmus
Original titleDe Libero Arbitrio
LanguageLatin
GenrePhilosophy, Theology
PublisherJohann Froben
Publication date
September 1524
Preceded byAssertio omnium articulorum M. Lutheri per bullam Leonis X 
Followed byOn the Bondage of the Will 

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. It was written to call out Martin Luther's revival of John Wycliffe's teaching that "everything happens by absolute necessity".

Erasmus' civil but deliberately provocative book mixes evangelical concerns that God has revealed himself as merciful not arbitrary ("nobody should despair of forgiveness by a God who is by nature most merciful" I.5.) and the conclusion in the Epilogue that where there are scriptures both in favour and against, theologians should moderate their opinions or hold them moderately: dogma is created by the church not theologians.:86 In his view, a gently-held synergism mediates the scriptural passages best, and moderates the exaggerations of both Pelagius (humans meriting or not requiring grace for salvation) and Manichaeus (two Gods: one good, one bad).

In response, Luther wrote his important work On the Bondage of the Will (1525), against which Erasmus in turn wrote the two-volume book Hyperaspistes (1526, 1528), which Luther did not respond to.