Alvin Plantinga's free-will defense is a logical argument developed by the American analytic philosopher Alvin Plantinga and published in its final version in his 1977 book God, Freedom, and Evil. Plantinga's argument is a defense against the logical problem of evil as formulated by the philosopher J. L. Mackie beginning in 1955. Mackie's formulation of the logical problem of evil argued that three attributes ascribed to God are logically incompatible with the existence of evil.