Réginald Marie Garrigou-Lagrange OP (French: [gaʁigu lagʁɑ̃ʒ]; 21 February 1877 – 15 February 1964) was a French Dominican friar, philosopher and theologian. Garrigou-Lagrange was a neo-Thomist theologian, recognized along with Édouard Hugon and Martin Grabmann as distinguished theologians of the 20th century. As professor at the Pontifical University of Saint Thomas Aquinas, he taught dogmatic and spiritual theology in Rome from 1909 to 1959. There he wrote The Three Ages of the Interior Life (Les trois âges de la vie intérieure) in 1938. He is best known for his spiritual theology. His magnum opus in the field is The Three Ages of the Interior Life (Les trois ages de la vie intérieure), in which he propounded the thesis that infused contemplation and the resulting mystical life are in the normal way of holiness of Christian perfection. This influenced the section entitled "Chapter V: The Universal Call to Holiness in the Church" in the Second Vatican Council's Dogmatic Constitution on the Church, Lumen gentium. He synthesized the highly abstract writings of St. Thomas Aquinas with the experiential writings of St. John of the Cross, attempting to show they are in perfect harmony with each other. Father Garrigou-Lagrange, the leading proponent of "strict observance Thomism", attracted wider attention when in 1946 he wrote against the [[Nouvelle Théologie]] theological movement, criticizing elements of it as Modernist. He is also said to be the drafter of Pope [[Pius XII]]'s 1950 encyclical [[Humani generis]], subtitled "Concerning Some False Opinions Threatening to Undermine the Foundations of Catholic Doctrine". In politics, like many neo-scholastic theologians of his time, Garrigou-Lagrange was a strong supporter of the far-right movement Action Française and he also sympathized with Vichy France. In 1941 he praised the French collaborationist regime and its Chief of State Pétain in a letter written to his former disciple Jacques Maritain: "I am entirely with the Marshal, I see him as the Father of the patrie, blessed with a good sense verging on genius, and as a truly providential man".