"A man has free choice to the extent that he is rational."
It was the famous Roman Catholic theologian Thomas Aquinas.
Saint Thomas Aquinas (also Thomas of Aquin, or Aquino; c. 1225 – 7 March 1274) was an Italian Catholic priest in the Order of Preachers, a philosopher and theologian in the scholastic tradition, known as Doctor Angelicus, Doctor Universalis and Doctor Communis. He is the foremost classical proponent of natural theology, and the father of the Thomistic school of philosophy and theology. St. Thomas is held in the Roman Catholic Church to be the model teacher for those studying for the priesthood. The work for which he is best-known is the Summa Theologica. (from Wikipedia)