Michel-Louis Guérard des Lauriers

On 29 July 1931, des Lauriers was ordained a priest.

He was an Invited Speaker of the International Congress of Mathematicians (ICM) in 1932 in Zurich. In 1933, he became a professor of philosophy at the Dominican school of theology, Le Saulchoir, in Belgium. In 1940, he received a doctorate in mathematics with thesis Sur les systèmes différentiels du second ordre qui admettent un groupe continu fini de transformations.[4]

Under Pope Pius XII, he served as a professor at the Pontifical Lateran University in Rome.[5] Some time prior to 1950, he was an advisor to the same pope on the dogma of the Assumption of Mary (proclaimed in Munificentissimus Deus).[6] From 1954 until 1955 he served as personal Father Confessor to the same pope, before being replaced by Augustin Bea.

With the advent of the Second Vatican Council in the 1960's, des Lauriers became concerned with events taking place in the Church. He was the main intellectual force behind the famous critical study of the Mass of Paul VI (Novus Ordo Mass) called the Ottaviani Intervention, presented to Paul VI in October 1969.[7][8][9] In 1970, Pope Paul VI made public a document demanding the resignation of certain conservative professors at the pontifical universities of Rome, among them was des Lauriers.

In 1979, worried about Archbishop Marcel Lefebvre and a possible deal with the Vatican among other things, des Lauriers wrote to Lefebvre warning him.[10][11]

Des Lauriers then became a lecturer and professor at the International Seminary of Saint Pius X of Lefebvre's Society of Saint Pius X (SSPX) in Écône, Switzerland. He then presented his thesis that the Holy See might be vacant because Pope Paul VI was guilty of teaching heresy (see sedevacantism). Because of this view, he was removed from his seminary teaching post by Lefebvre in 1977.

Des Lauriers further developed his beliefs on the current state of the papacy, arguing that the necessary conclusion from Paul VI teaching heresy in the context of the Magisterium, was that he could not be a true pope, being only pope materially (papa materialiter) and not formally, known as the Thesis of Cassiciacum.

Des Lauriers further believed that the new rites of ordination and episcopal consecration (newest Pontificale Romanum, new forms by promulgation of 18 June 1968) promulgated by Paul VI were doubtfully valid (or even outright invalid) and therefore it was necessary to take action to secure a valid apostolic succession for the preservation of the (Latin Rite) Roman Catholic Church. He began discussions with Doctor Eberhard Heller and Doctor Kurt Hiller, German sedevacantists who were harboring Ngô Đình Thục (1897–1984), former archbishop of Huế, Vietnam, and after des Lauriers agreed to abate his sedeprivationism and adhere to the theoretical tenets of absolute/totalist sedevacantism, it was agreed that the archbishop would consecrate him a bishop.[12]

On 7 May 1981, after long consideration, des Lauriers was consecrated a bishop by Thuc in Toulon, France.

Des Lauriers consecrated three bishops: Günther Storck, a German, on 30 April 1984; Robert McKenna, an American, on 22 August 1986; and Franco Munari, an Italian, on 25 November 1987.

Des Lauriers died in Cosne-sur-Loire, France, on 27 February 1988, at the age of 89. He is buried in Raveau, France.[2]

There are currently three bishops who adhere to his Thesis of Cassicicum: Bishop Geert Stuyver (a Belgian) of the Istituto Mater Boni Consilii (IMBC), which is based in Italy, and where des Lauriers is highly commemorated, and Bishop Donald Sanborn and Bishop Joseph Selway (both Americans) of the Roman Catholic Institute (RCI), which is based in the United States.

• Le Saint-Esprit, âme de l'Eglise, Étiolles, Seine et Oise : Monastère de la Croix, 1948.
• Garabandal, S.l., 1965.
• Lettera ad un religioso di Simone Weil ; trad. di Mariella Bettarini. Risposta alla Lettera ad un religioso di Guérard des Lauriers ; trad. di Carmen Montesano (Lettre à un religieux), Torino : Borla, 1970.
• La Mathématique, les mathématiques, la mathématique moderne, Paris : Doin, 1972.
• Homélie (prononcée le 15 mai 1971 pour l'anniversaire de la mort de l'amiral de Penfentenyo de Kervéréguin), Versailles : R.O.C., 1973.
• La Charité de la vérité, Villegenon : Sainte Jeanne d'Arc, 1985.
• La Présence réelle du Verbe incarné dans les espèces consacrées, Villegenon : Sainte Jeanne d'Arc, 1987.

• Louis-Marie de Blignières, Le mystère de l'être. L'approche thomiste de Guérard des Lauriers, Paris, J. Vrin, 2008.