Friedrich Bernard Christian Maassen
United Sees of Macerata and Tolentino
Vicariate Apostolic of Mackenzie
Marie-Edmé-Patrice-Maurice de MacMahon
Joseph-Anna-Marie de Moyria de Mailla
François-Pierre-Gonthier Maine de Biran
Françoise, Marquise de Maintenon
Joseph-Marie, Comte de Maistre
Marcellinus of Civezza, O.F.M.
Margaret of the Blessed Sacrament
Prefecture Apostolic of Mariana Islands
Congregation of the Missionaries of Mariannhill
Sts. Maris, Martha, Audifax, and Abachum
Lucius Perpetuus Aurelianus Marius Maximus
Vicariate Apostolic of Marquesas Islands
Moral and Canonical Aspect of Marriage
Diocese of Marseilles (Massilia)
Vicariate Apostolic of the Marshall Islands
Diocese of Marsico Nuovo and Potenza
Luigi Ferdinando, Count de Marsigli
Missionaries of the Company of Mary
Servants of Mary (Order of Servites)
Society of Mary (Marist Fathers)
St. Mary Frances of the Five Wounds of Jesus
Richard Angelus a S. Francisco Mason
Devises and Bequests for Masses (United States)
Feast of the Maternity of the Blessed Virgin Mary
Marcus Aurelius Valerius Maximianus
Caius Julius Verus Maximinus Thrax
Prefecture Apostolic of Mayotte, Nossi-Bé, and Comoro
Charles Joseph Eugene de Mazenod
Abbey and Congregation of Melk
Vicariate Apostolic of Méndez and Gualaquiza
Francisco Sarmiento de Mendoza
Corporal and Spiritual Works of Mercy
Sisters of Mercy of St. Borromeo
Frédéric-François-Xavier Ghislain de Mérode
Delegation Apostolic of Mesopotamia, Kurdistan, and Armenia
Metal-Work in the Service of the Church
Prince Klemens Lothar Wenzel von Metternich
Francis, Joseph, and Paul Mezger
Military Orders of St. Michael
Giovanni Francesco Pico della Mirandola
Congregation of the Sisters of Misericorde
Prefecture Apostolic of Misocco and Calanca
Congregation of Priests of the Mission
Congregation of Missionaries of St. Charles Borromeo
Missionaries of St. Francis de Sales of Annecy
Missionary Society of St. Paul the Apostle
Mission Indians (of California)
Catholic Indian Missions of Canada
Catholic Indian Missions of the United States
François-Napoléon-Marie Moigno
Diocese of Molfetta, Terlizzi, and Giovinazzo
Jean-Baptiste Poquelin Molière
Principality and Diocese of Monaco
Canonical Erection of a Monastery
Monophysites and Monophysitism
Monothelitism and Monothelites
Montagnais Indians (Chippewayans)
Charles-Forbes-René, Comte de Montalembert
Marquis de Louis-Joseph Montcalm-Gozon
Diocese of Monterey and Los Angeles
Charles-Louis de Secondat, Baron de Montesquieu
Anne, First Duke of Montmorency
Alexis-François Artaud de Montor
Antoine-Jean-Baptiste-Robert Auget, Baron de Montyon
Dioceses of Mostar and Markana-Trebinje
Feast of the Most Pure Heart of Mary
Toribio de Benavente Motolinia
Congregations of Mount Calvary
Feast of Our Lady of Mount Carmel
Karl Ernst, Freiherr von Moy de Sons
Johann Chrysostomus Wolfgang Amadeus Mozart
St. Clair Augustine Mulholland
Baron Eligius Franz Joseph von Münch-Bellinghausen
Archdiocese of Munich-Freising
French theologian, philosopher, and mathematician; b. 8 September, 1588, near Oizé (now Department of Sarthe); d. 1 September, 1648 at Paris. He studied at Le Mans and at the Jesuit College of La Flèche, where a lifelong friendship with Descartes, his fellow student, originated. Mersenne entered the novitiate of the Minims at Nigeon near Paris (1611), was sent to Nevers as professor of philosophy (1614-1620), and returned to Paris. His first publications were theological and polemical studies against Atheism and Scepticism, but later, Mersenne devoted his time almost exclusively to science, making personal experimental researches, and publishing a number of works on mathematical sciences. His chief merit, however, is rather the encouragement which he gave to scientists of his time, the interest he took in their work, and the stimulating influence of his suggestions and questions. Gassendi and Galileo were among his friends; but, above all, Mersenne is known to-day as Descartes's friend and adviser. In fact, when Descartes began to lead a free and dissipated life, it was Mersenne who brought him back to more serious pursuits and directed him toward philosophy. In Paris, Mersenne was Descartes's assiduous correspondent, auxiliary, and representative, as well as his constant defender. The numerous and vehement attacks against the "Meditations" seem, for a moment, to have aroused Mersenne's suspicions; but Descartes's answers to his critics gave him full satisfaction as to his friend's orthodoxy and sincere Christian spirit. Mersenne asked that, after his death, an autopsy be made on his body, so as to serve to the last the interests of science.
Mersenne's works are: "Quæstiones celeberrimæ in Genesim" (Paris, 1623), against Atheists and Deists; a part only has been published, the rest being still in manuscript, as also a "Commentary on St. Matthew's Gospel"; "L'impiété des déistes et des plus subtils libertins découverte et réfutée par raisons de théologie et de philosophie" (Paris, 1624); "La vérité des sciences contre les sceptiques et les pyrrhoniens" (Paris, 1625); "Questions theólogiques, physiques, morales et mathématiques" (Paris, 1634); "Questions inouïes, ou récréations des savants" (Paris, 1634); "Les mécaniques de Galilée" (Paris, 1634), a translation from the Italian; "Harmonie universelle, contenant la théorie et la pratique de la musique" (Paris, 1936-7); "Nouvelles découvertes de Galilée", and "Nouvelles pensées de Galilée sur les mécaniques" (Paris, 1639), both translations; "Cogitata physico-mathematica" (Paris, 1644); "Euclidis elementorum libri, Apollonii Pergæ conica, Sereni de sectione coni, etc." (Paris, 1626), selections and translations of ancient mathematicians, published again later with notes and additions under the title, "Universæ geometriæ mixtæque mathematicæ synopsis" (Paris, 1644).
DE COSTE, Vie du R. P. Mersenne (Paris, 1649); POTÉ Eloge de Mersenne (Le Mans, 1816); BAILLET, Vie de Descartes (Paris, 1691); HAURÉAU, Histoire littéraire de Maine, I, 321.
C. A. DUBRAY