The author investigates the problem whether it is possible to adopt two tenets at the same time: one saying that God possesses prior knowledge of future contingent events, especially human acts, and another one saying that humans can act freely. These problems are discussed in a historical perspective. He analyses the paradigmatic conception of Saint Augustine presented in the 'De libero arbitrio' and in the 'City of God'. Augustine's position is founded, most commentators would agree, on theological determinism which presupposes a deterministic conception of human will. An opposite view was propagated by Luis Molina who spurred a deep controversy in Christian philosophy and theology in seventeenth century France. The debate ended with an official condemnation of Jansenism (1713), the position that represented theological determinism. When it was rejected, the Molinists, or Jesuits, were left in the field as the winners of the debate. The author shows how the seventeenth century controversy continues to this day pinning advocates of God's intermediate knowledge (Alvin Plantinga) against opponents of that conception (R. Adams, W. Hasker). Today, however, the debate focuses on a logical problem rather than a purely theological one, and it concerns primarily counterfactuals of freedom, i.e. the question whether counterfactuals, such as 'Saul could have conquered the city if David had remained in Keilah' can be true at all.