Alvin Plantinga, the John A. O'Brien Professor of Philosophy at the University of Notre Dame, is widely considered one of the most important philosophical figures of the past century. A Calvinist, Plantinga successfully refuted the "logical problem of evil" in his work, God, Freedom, and Evil(1974), with what is known as the "Free Will Defense". In so doing, Plantinga forced the philosophic debate over the existence and nature of God away from logical refutation into arguments about the improbability of the existence an all-powerful, all-good God in light of the existence of evil. It is here that the new debate continues, thanks to Plantinga's work.

Plantinga's other philosophic contributions have been in the realm of defending Christian knowledge.