"---.  We say that Vatican II established itself as the anti-Church.  Consequently, whoever adheres to Vatican II, without restriction, by this fact alone detaches himself from the true Church of Christ.  No one can, at the same time, be Catholic and subscribe to everything established by the Second Vatican Council.  We would say that the best way to abandon the Church of Christ, Catholic, Apostolic and Roman, is to accept, without reservation, everything that the Second Vatican Council taught and proposed.  He is anti-Church. " [Mrgr de Castro-Mayer (1904-1991) – Heri and Hodie (journal of the priests of Campos) n°33 – September 1986]”

https://isidore.co/misc/Res%20pro%20Deo/Sel%20de%20la%20Terre/Sdt%20N%C2%B0037/Pr%C3%A9sentation%20du%20Cath%C3%A9chisme%20des%20v%C3%A9rit%C3%A9s%20opportunes.txt
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Presentation of the Catechism of Opportune Truths [Le Sel de la Terre digital ? Edition] of Mgr de Castro Mayer;  by His Exc. Mgr Licinio Rangel.

TO PRESENT this “Catechism” nothing is more appropriate than to transcribe a few points from the “Pastoral Letter on the Problems of the Modern Apostolate” which serves as its introduction. Here are some of the initial points of this magisterial and still relevant Pastoral Letter:
"Of all the duties incuмbent on a bishop, none surpasses in importance that of providing the sheep entrusted to him by the Holy Spirit, the salutary food of revealed truth. This obligation is particularly pressing today. For the immense crisis in which the world is struggling results, in the final analysis, from the fact that the thoughts and actions of men have been dissociated from the teachings and norms laid down by the Church, and only by a return of humanity to the true Faith that the remedy to this crisis can be found.  It is, in fact, of the highest importance to launch, united and disciplined, all the Catholic forces, the entire peaceful army of Christ the King, to the conquest of the peoples who groan in the shadow of death, deceived by heresy or schism, by the superstitions of ancient paganism or by the multiple idols of modern neopaganism. For this general offensive, so desired by the sovereign pontiffs, to be effective and victorious, it is important that the Catholic forces themselves remain pure of the errors they must combat. The preservation of the Faith among the children of the Church is a necessary and sovereign measure for the establishment of the reign of Christ on earth. History teaches us that the temptation against faith, always the same in its essential elements, presents itself in each era under a new aspect. Arianism, for example, which exerted such great seductive force in the 4th century, would have had little interest in the frivolous and Voltairian European of the 18th century; and the declared and radical atheism of the 19th century would have had little chance of success in the time of Wyclif and Jean Hus. Furthermore, the temptation against the faith has the habit of acting with different intensity in each generation. She manages to lead one completely towards heresy. To the other, without tearing it in a formal and declared way from the maternal bosom of the Church, it infuses its spirit, so that, in many Catholics who correctly recite the formulas of the faith and believe, sometimes sincerely, to adhere without restriction to the teachings of the ecclesiastical magisterium,  but their heart beats under the influx of doctrines condemned by the Church." *

Hence, the appropriateness of the method used by Mgr Antonio de Castro Mayer, juxtaposing "the doctrines that the Church has condemned", latent in the hearts of a large number, especially in these times of post-conciliar crisis, and the clear affirmation of the authentic doctrine of the ecclesiastical magisterium.
If the crisis designated by Dom de Castro Mayer in the middle of the previous century was already serious, what can we say about it after three decades of conciliar subversion? However, although it has been in existence for half a century, the Pastoral Letter of Mgr de Castro Mayer, with the Catechism of Opportune Truths which Oppose Contemporary Errors, retains all its relevance, because the “contemporary errors” that these “Opportune Truths” are fighting  have only gotten worse with the conciliar crisis. We can even say that this is nothing other than an explosion of the errors then denounced by Dom Antonio de Castro Mayer.
It is enough to recall one aspect: the conciliar liturgical reform, with all its devastating character, was contained in germ in the errors of liturgicalism condemned in the proposals of the Pastoral Letter of Dom de Castro Mayer.
Congratulations, therefore, to those responsible for the prestigious magazine ' Le Sel de la Terre' for the initiative of this publication on the occasion of the tenth anniversary of its author’s call to God.
† Dom Licinio Rangel  THE SALT OF THE EARTH Nº 37, SUMMER 2001


* [, Not certain where the quotation of +Castro Mayer's  ends. ED.]

On Jan. 1, 2014, Le Sel de la Terre printed a pamphlet, 128 pp. in French: Lettre Pastorale sur les Problemes de l'Apostolat Moderne, et Catechisme des Verités Opportunes qui s'opposent aux erreurs Contemporaines .., ISBN: 9782916139029

+ de Castro Mayer wrote this Catechism Jan 6, 1953
Dominicans of Avrille published it in Sel de la Terre, in Edition Numero 37 -41, Summer 2001