In the course of time, namely from the beginnings of the human race until the coming and preaching of Jesus Christ, He Himself taught man the duties which a rational creature owes to its Creator […] From which it follows that there can be no true religion other than that which is founded on the revealed word of God: which revelation, begun from the beginning and continued under the Old Law, Christ Jesus Himself under the New Law perfected. Now, if God has spoken (and it is historically certain that He has truly spoken), all must see that it is man’s duty to believe absolutely God’s revelation and to obey implicitly His commands; that we might rightly do both, for the glory of God and our own salvation, the Only-begotten Son of God founded His Church on earth. (Pius XI. Encyclical Mortalium animos, no. 7, January 6, 1928)

First, let us examine that liberty in individuals which is so opposed to the virtue of religion, namely, the liberty of worship, as it is called. This is based on the principle that every man is free to profess as he may choose any religion or none. […] And if it be asked which of the many conflicting religions it is necessary to adopt, reason and the natural law unhesitatingly tell us to practice that one which God enjoins, and which men can easily recognize by certain exterior notes, whereby Divine Providence has willed that it should be distinguished, because, in a matter of such moment, the most terrible loss would be the consequence of error. Wherefore, when a liberty such as We have described is offered to man, the power is given him to pervert or abandon with impunity the most sacred of duties, and to exchange the unchangeable good for evil; which, as We have said, is no liberty, but its degradation, and the abject submission of the soul to sin. (Leo XIII. Encyclical Libertas praestantissimum, no. 19, June 20, 1888)

Again, as all who offer themselves are received whatever may be their form of religion, they thereby teach the great error of this age-that a regard for religion should be held as an indifferent matter, and that all religions are alike. This manner of reasoning is calculated to bring about the ruin of all forms of religion, and especially of the Catholic religion, which, as it is the only one that is true, cannot, without great injustice, be regarded as merely equal to other religions. (Leo XIII. Encyclical Humanum genus, no. 6, April 20, 1884)

But at the same time Catholics are bound to profess that through the gift of God’s mercy they belong to that Church which Christ founded and which is governed by the successors of Peter and the other Apostles, who are the depositories of the original Apostolic tradition, living and intact, which is the permanent heritage of doctrine and holiness of that same Church. The followers of Christ are therefore not permitted to imagine that Christ’s Church is nothing more than a collection (divided, but still possessing a certain unity) of Churches and ecclesial communities. Nor are they free to hold that Christ’s Church nowhere really exists today and that it is to be considered only as an end which all Churches and ecclesial communities must strive to reach. (Congregation for the Doctrine of the Faith. Declaration Mysterium Ecclesiae, no. 1, June 24, 1973)

[The definition of faith] Since man is wholly dependent on God as his Creator and Lord, and since created reason is completely subject to uncreated truth, we are bound by faith to give full obedience of intellect and will to God who reveals [can. 1]. But the Catholic Church professes that this faith, which ‘is the beginning of human salvation’ [cf. no. 801], is a supernatural virtue by which we, with the aid and inspiration of the grace of God, believe that the things revealed by Him are true, not because the intrinsic truth of the revealed things has been perceived by the natural light of reason, but because of the authority of God Himself who reveals them, who can neither deceive nor be deceived [can. 2]. For, ‘faith is,’ as the Apostle testifies, ‘the substance of things to be hoped for, the evidence of things that appear not’ (Heb 11:1). (Denzinger-Hünermann 3008. Vatican Council I, Session III, Dogmatic constitution concerning the Catholic Faith, April 24, 1870)

When Saint Peter confessed that Jesus is the Christ, the Son of the living God, Jesus declared to him that this revelation did not come ‘from flesh and blood’, but from ‘my Father who is in heaven’ (Mt 16:17; cf. Gal 1:15; Mt 11:25). Faith is a gift of God, a supernatural virtue infused by him. ‘Before this faith can be exercised, man must have the grace of God to move and assist him; he must have the interior helps of the Holy Spirit, who moves the heart and converts it to God, who opens the eyes of the mind and ‘makes it easy for all to accept and believe the truth.’ (Dei Verbum, no. 5) (Catechism of the Catholic Church, no. 153)

Now man’s happiness is twofold, as was also stated above (q. 5, a. 5). One is proportionate to human nature, a happiness, to wit, which man can obtain by means of his natural principles. The other is a happiness surpassing man’s nature, and which man can obtain by the power of God alone, by a kind of participation of the Godhead, about which it is written (2Pet 1:4) that by Christ we are made ‘partakers of the Divine nature.’ And because such happiness surpasses the capacity of human nature, man’s natural principles which enable him to act well according to his capacity, do not suffice to direct man to this same happiness. Hence it is necessary for man to receive from God some additional principles, whereby he may be directed to supernatural happiness, even as he is directed to his connatural end, by means of his natural principles, albeit not without Divine assistance. Such like principles are called ‘theological virtues’. […] A certain nature may be ascribed to a certain thing in two ways. First, essentially: and thus these theological virtues surpass the nature of man. Secondly, by participation, as kindled wood partakes of the nature of fire: and thus, after a fashion, man becomes a partaker of the Divine Nature, as stated above: so that these virtues are proportionate to man in respect of the Nature of which he is made a partaker. (Saint Thomas Aquinas. Summa Theologica, I-II, q. 62, a. 1)

That which is above man’s nature is distinct from that which is according to his nature. But the theological virtues are above man’s nature; while the intellectual and moral virtues are in proportion to his nature, as clearly shown above (q. 58, a. 3). (Saint Thomas Aquinas. Summa Theologica, I-II, q. 62, a. 2)

The object of faith is, in a way, the First Truth, in as much as nothing comes under faith except in relation to God, even as the object of the medical art is health, for it considers nothing save in relation to health. […] Things concerning Christ’s human nature, and the sacraments of the Church, or any creatures whatever, come under faith, in so far as by them we are directed to God, and in as much as we assent to them on account of the Divine Truth. (Saint Thomas Aquinas. Summa Theologica, II-II, q. 1, a. 1)

Now it has been stated (a. 1) that the formal aspect of the object of faith is the First Truth; so that nothing can come under faith, save in so far as it stands under the First Truth, under which nothing false can stand, as neither can non-being stand under being, nor evil under goodness. It follows therefore that nothing false can come under faith. (Saint Thomas Aquinas. Summa Theologica, II-II, q. 1, a. 3)

The Apostle says (1Thess 2:15): ‘When you had received of us the word of the hearing,’ i.e. by faith . . . ‘you received it not as the word of men, but, as it is indeed, the word of God.’ Now nothing is more certain than the word of God. Therefore science is not more certain than faith; nor is anything else. (Saint Thomas Aquinas. Summa Theologica, II-II, q. 4, a. 8)

Unbelief may be taken in two ways: first, by way of pure negation, so that a man be called an unbeliever, merely because he has not the faith. Secondly, unbelief may be taken by way of opposition to the faith; in which sense a man refuses to hear the faith, or despises it, according to Isaiah 53:1: ‘Who hath believed our report?’ It is this that completes the notion of unbelief, and it is in this sense that unbelief is a sin. If, however, we take it by way of pure negation, as we find it in those who have heard nothing about the faith, it bears the character, not of sin, but of punishment, because such like ignorance of Divine things is a result of the sin of our first parent. […] Unbelief, in so far as it is a sin, arises from pride, through which man is unwilling to subject his intellect to the rules of faith, and to the sound interpretation of the Fathers. Hence Gregory says (Moral.31, 45) that ‘presumptuous innovations arise from vainglory.’ (Saint Thomas Aquinas. Summa Theologica, II-II, q. 10, a. 1)

Every sin consists formally in aversion from God, as stated above (I-II, q. 71, a. 6; I-II, q. 73, a. 3, ad 3). Hence the more a sin severs man from God, the graver it is. Now man is more than ever separated from God by unbelief, because he has not even true knowledge of God: and by false knowledge of God, man does not approach Him, but is severed from Him. (Saint Thomas Aquinas. Summa Theologica II-II, q. 10, a. 3)

Nor is it possible for one who has a false opinion of God, to know Him in any way at all, because the object of his opinion is not God. Therefore it is clear that the sin of unbelief is greater than any sin that occurs in the perversion of morals. This does not apply to the sins that are opposed to the theological virtues, as we shall stated further on. (Saint Thomas Aquinas. Summa Theologica, II-II, q. 10, a. 3)

Mortal sin takes away sanctifying grace, but does not wholly corrupt the good of nature. Since therefore, unbelief is a mortal sin, unbelievers are without grace indeed, yet some good of nature remains in them. Consequently it is evident that unbelievers cannot do those good works which proceed from grace, viz. meritorious works; yet they can, to a certain extent, do those good works for which the good of nature suffices. Hence it does not follow that they sin in everything they do; but whenever they do anything out of their unbelief, then they sin. For even as one who has the faith, can commit an actual sin, venial or even mortal, which he does not refer to the end of faith, so too, An unbeliever can do a good deed in a matter which he does not refer to the end of his unbelief. […] Faith directs the intention with regard to the supernatural last end: but even the light of natural reason can direct the intention in respect of a connatural good. (Saint Thomas Aquinas. Summa Theologica, II-II, q. 10, a. 4, sol. ad. 2)

For this reason, the distinction between theological faith and belief in the other religions, must be firmly held. […] This distinction is not always borne in mind in current theological reflection. Thus, theological faith (the acceptance of the truth revealed by the One and Triune God) is often identified with belief in other religions, which is religious experience still in search of the absolute truth and still lacking assent to God who reveals himself. This is one of the reasons why the differences between Christianity and the other religions tend to be reduced at times to the point of disappearance. (Congregation for the Doctrine of the Faith. Declaration Dominus Iesus, no. 7, August 6, 2000)

[…] but should remember that the followers of every heresy extract from inspired scripture the occasion of their error, and that all heretics corrupt the true expressions of the Holy Spirit with their own evil minds and they draw down on their own heads an inextinguishable flame. (Council of Ephesus. Letter from Cyril to John of Antioch concerning peace, 431)

The Church holds that these multitudes have the right to know the riches of the mystery of Christ – riches in which we believe that the whole of humanity can find, in unsuspected fullness, everything that it is gropingly searching for concerning God, man and his destiny, life and death, and truth. […] In other words, our religion effectively establishes with God an authentic and living relationship which the other religions do not succeed in doing, even though they have, as it were, their arms stretched out towards heaven. (Paul VI. Apostolic exhortation Evangelii nuntiandi, no. 53, December 8, 1975)

No one will be saved who, knowing the Church to have been divinely established by Christ, nevertheless refuses to submit to the Church or withholds obedience from the Roman pontiff, the vicar of Christ on earth […] [Pius XII] mentions those who ‘are related to the Mystical Body of the Redeemer by a certain unconscious yearning and desire’, and these he by no means excludes from eternal salvation, but who, on the other hand, as he states, are in a condition ‘in which they cannot be sure of their own eternal salvation’ since ‘they are deprived of so many and such great heavenly gifts (and) helps that can only be enjoyed in the Catholic Church.’ With these wise words he condemns both those who exclude from eternal salvation all united to the Church only by implicit desire and those who falsely assert that men can be saved equally well in every religion. (Denzinger-Hünermann 3867.3871-3872. Letter of the Holy Office to the Archbishop of Boston, August 8, 1949)

For since they hold it for certain that men destitute of all religious sense are very rarely to be found, they seem to have founded on that belief a hope that the nations, although they differ among themselves in certain religious matters, will without much difficulty come to agree as brethren in professing certain doctrines, which form as it were a common basis of the spiritual life. For which reason conventions, meetings and addresses are frequently arranged by these persons, at which a large number of listeners are present, and at which all without distinction are invited to join in the discussion, both infidels of every kind, and Christians, even those who have unhappily fallen away from Christ or who with obstinacy and pertinacity deny His divine nature and mission. Certainly such attempts can nowise be approved by Catholics, founded as they are on that false opinion which considers all religions to be more or less good and praiseworthy, since they all in different ways manifest and signify that sense which is inborn in us all, and by which we are led to God and to the obedient acknowledgment of His rule. Not only are those who hold this opinion in error and deceived, but also in distorting the idea of true religion they reject it, and little by little. turn aside to naturalism and atheism, as it is called; from which it clearly follows that one who supports those who hold these theories and attempt to realize them, is altogether abandoning the divinely revealed religion. (Pius XI. Encyclical Mortalium animos, no. 2, January 6, 1928)

There are no lack of those who wish to interpret the missionary action [of the Church] as an attempt to impose on others one’s own convictions and options, in contrast with a certain modern spirit, which boasts, as though it was a definitive conquest, of an absolute liberty of thought and personal conscience. According to this perspective, evangelizing activity should be substituted with an interreligious dialogue, which would consist in an exchange of opinions and information, whereby each party would expose his own ‘creed’ and be enriched by the thoughts of others, without any preoccupation of arriving at conclusions. […] Consequently the path that each one wishes to follow according to one’s own education and religious tradition would be respected. But this conception is irreconcilable with the commandment of Christ to the Apostles (cf. Mt 28:19-20; Mk 16:15), transmitted by the Church […] [The Council] confirmed at the same time the role of the Church, in which it is necessary that man enter and persevere, if he wishes to be saved (Ad gentes, no. 7) […] This traditional doctrine of the Church exposes the inconsistency and superficiality of a relativistic and irenic attitude, regarding the way of salvation in a religion other than that founded in the faith in Christ. (John Paul II. General Audience, no. 1-2, May 10, 1995)

Whoever knows the Old and New Testaments, and then reads the Koran, clearly sees the process by which it completely reduces Divine Revelation. It is impossible not to note the movement away from what God said about Himself, first in the Old Testament through the Prophets, and then finally in the New Testament through His Son. In Islam all the richness of God’s self-revelation, which constitutes the heritage of the Old and New Testaments, has definitely been set aside. Some of the most beautiful names in the human language are given to the God of the Koran, but He is ultimately a God outside of the World, a God who is only Majesty, never Emmanuel, God-with-us. Islam is not a religion of redemption. There is no place for the Cross and the Resurrection. Jesus is mentioned, but only as preparatory prophet for the last prophet, Mohammed. Mary, his virginal Mother, is also recalled: but she is entirely absent from the drama of the Redemption. That is why not only theology, but also the anthropology of Islam is very far from the Christian. (John Paul II. Crossing the Threshold of Hope, 1994, pg. 92)

There are many other extraordinary and quite ridiculous things in this book which he boasts was sent down to him from God. But when we ask: ‘And who is there to testify that God gave him the book? And which of the prophets foretold that such a prophet would rise up? They are at a loss. And we remark that Moses received the Law on Mount Sinai, with God appearing in the sight of all the people in cloud, and fire, and darkness, and storm. And we say that all the Prophets from Moses on down foretold the coming of Christ and how Christ God (and incarnate Son of God) was to come and to be crucified and die and rise again, and how He was to be the judge of the living and dead. Then, when we say: How is it that this prophet of yours did not come in the same way, with others bearing witness to him? And how is it that God did not in your presence present this man with the book to which you refer, even as He gave the Law to Moses, with the people looking on and the mountain smoking, so that you, too, might have certainty? They answer that God does as He pleases. This we say, ‘We know, but we are asking how the book came down to your prophet. Then they reply that the book came down to him while he was asleep. Then we jokingly say to them that, as long as he received the book in his sleep and did not actually sense the operation, then the popular adage applies to him (which runs: You’re spinning me dreams.) (Saint John Damascene. On Heresies, no. 105, PG 94, 766)

But that which has already been written is sufficient as the conclusion of this article, which is so important for your salvation; which is to say, for the destruction of the perverse sect of Mohammed. Because if we have proven that the finality that it proposes is entirely bestial, and unworthy of the authority of man; and if its author was an adulterous man, a perjurer, a thief, a murderer, a blasphemer, and most ignorant in human and divine letters; and if all the things contained in this his law were fables in philosophy and errors in theology, even for those who do not possess the light of reason, and the customs he teaches are a school of bestial vices; and he did not prove this his new sect with any motive, neither supernatural with miracles nor natural with reasons, but solely spread it by the force of arms, violence, fictions, lies, and carnal license, what remains other than it is a sect that is impious, blasphemous and vicious, an invention of the devil, and the direct way to the fires of hell, and that it does not even merit the name of being called a religion. (Saint John de Ribera. Catechism for the Instruction of the New Converts of the Moors, 1599 AD)

[…] the Turks and other infidels […] They treat the way of true light and salvation with complete contempt and totally unyielding blindness; they attack the life-giving cross on which our Saviour willed to accept death so that by dying he might destroy death, and by the ineffable mystery of his most holy life he might restore life; and they make themselves hateful enemies of God and most bitter persecutors of the Christian religion. Strengthened by defences not only spiritual but also temporal, we may be able, under God’s guidance and favour, to oppose the bitter and frequent sallies by which, in wild rage, they move savagely amidst Christian blood. (Lateran Council V. Session XII, March 16, 1517)

It is an insult to the holy name and a disgrace to the Christian faith that in certain parts of the world subject to Christian princes where Saracens live, sometimes apart, sometimes intermingled with Christians, the Saracen priests commonly called Zabazala, in their temples or mosques, in which the Saracens meet to adore the infidel Mahomet, loudly invoke and extol his name each day at certain hours from a high place, in the hearing of both Christians and Saracens and there make public declarations in his honour. There is a place, moreover, where once was buried a certain Saracen whom other Saracens venerate as a saint. A great number of Saracens flock there quite openly from far and near. This brings disrepute on our faith and gives great scandal to the faithful. These practices cannot be tolerated any further without displeasing the divine majesty. We therefore, with the sacred council’s approval, strictly forbid such practices henceforth in Christian lands. […] [We enjoin on catholic princes] They are to remove this offence altogether from their territories and take care that their subjects remove it, so that they may thereby attain the reward of eternal happiness. They are to forbid expressly the public invocation of the sacrilegious name of Mahomet. (Council of Vienne. Decree, no. 25, January 13, 1313)

Indeed, some prayers and rituals of the other religions may assume a role of preparation for the Gospel, in that they are occasions or pedagogical helps in which the human heart is prompted to be open to the action of God. One cannot attribute to these, however, a divine origin or an ex opere operato salvific efficacy, which is proper to the Christian sacraments. Furthermore, it cannot be overlooked that other rituals, insofar as they depend on superstitions or other errors (cf. 1Cor 10:20-21), constitute an obstacle to salvation. (Congregation for the Doctrine of the Faith. Declaration Dominus Iesus, no. 21, August 6, 2000)

‘The Catholic Church is alone in keeping the true worship. This is the fount of truth, this the house of Faith, this the temple of God: if any man enter not here, or if any man go forth from it, he is a stranger to the hope of life and salvation. Let none delude himself with obstinate wrangling. For life and salvation are here concerned, which will be lost and entirely destroyed, unless their interests are carefully and assiduously kept in mind’ (Divin. Instit. Iv, 30. 11-12). (Pius XI. Encyclical Mortalium animos, no. 11, January 6, 1928)

Prayer is both a gift of grace and a determined response on our part. It always presupposes effort. The great figures of prayer of the Old Covenant before Christ, as well as the Mother of God, the saints, and he himself, all teach us this: prayer is a battle. Against whom? Against ourselves and against the wiles of the tempter who does all he can to turn man away from prayer, away from union with God. We pray as we live, because we live as we pray. If we do not want to act habitually according to the Spirit of Christ, neither can we pray habitually in his name. The ‘spiritual battle’ of the Christian’s new life is inseparable from the battle of prayer. (Catechism of the Catholic Church, no. 2725)

Obviously we cannot agree with these various forms of religion, [Judaism, moslem religion and Afro-Asiatic) nor can we adopt an indifferent or uncritical attitude toward them on the assumption that they are all to be regarded as on an equal footing, and that there is no need for those who profess them to enquire whether or not God has Himself revealed definitively and infallibly how He wishes to be known, loved, and served. Indeed, honesty compels us to declare openly our conviction that the Christian religion is the one and only true religion, and it is our hope that it will be acknowledged as such by all who look for God and worship Him. (Paul VI. Encyclical Ecclesiam suam, no. 40, August 6, 1964)

[For the Modernist] In the religious sentiment one must recognize a kind of intuition of the heart which puts man in immediate contact with the very reality of God […] It is this experience which, when a person acquires it, makes him properly and truly a believer. How far off we are here from Catholic teaching we have already seen in the decree of the Vatican Council. […] Here it is well to note at once that, given this doctrine of experience united with the other doctrine of symbolism, every religion, even that of paganism, must be held to be true. What is to prevent such experiences from being met within every religion? In fact that they are to be found is asserted by not a few. And with what right will Modernists deny the truth of an experience affirmed by a follower of Islam? With what right can they claim true experiences for Catholics alone? Indeed Modernists do not deny but actually admit, some confusedly, others in the most open manner, that all religions are true. That they cannot feel otherwise is clear. For on what ground, according to their theories, could falsity be predicated of any religion whatsoever? (Pius X. Encyclical Pascendi Dominici gregis, no. 14, September 8, 1907)

Christ is the one Savior of all, the only one able to reveal God and lead to God. […] No one, therefore, can enter into communion with God except through Christ, by the working of the Holy Spirit. Christ’s one, universal mediation, far from being an obstacle on the journey toward God, is the way established by God himself, a fact of which Christ is fully aware. Although participated forms of mediation of different kinds and degrees are not excluded, they acquire meaning and value only from Christ’s own mediation, and they cannot be understood as parallel or complementary to his. (John Paul II. Encyclical Redemptoris missio, no. 5, December 7, 1990)

To hold, therefore, that there is no difference in matters of religion between forms that are unlike each other, and even contrary to each other, most clearly leads in the end to the rejection of all religion in both theory and practice. And this is the same thing as atheism, however it may differ from it in name. Men who really believe in the existence of God must, in order to be consistent with themselves and to avoid absurd conclusions, understand that differing modes of divine worship involving dissimilarity and conflict even on most important points cannot all be equally probable, equally good, and equally acceptable to God. (Leo XIII. Encyclical Immortale Dei, no. 14, November 1, 1885)

The manner of praying is also a matter of the highest moment. Though prayer in itself is good and salutary, yet if not performed in a proper manner it is unavailing. Often we do not obtain what we ask, because, in the words of St. James, we ask amiss. […] This practice of praying in spirit is peculiar to Christians, and is not at all used by infidels. Of these Christ the Lord has said: When you pray, speak not much, as the heathens; for they think that in their much speaking they may be heard. Be not ye, therefore, like to them, for your Father knoweth what is needful for you before you ask him. […] Neither do the prayers of the hypocrite proceed from the heart; and against the imitation of their example, Christ the Lord warns us in these words: ‘When ye pray, ye shall not be as the hypocrites that love to stand and pray in the synagogues, and corners of the streets, that they may be seen by men. Amen I say, to you they have received their reward. But thou, when thou shalt pray, enter into thy chamber, and having shut the door, pray to thy Father in secret; and thy Father who seeth in secret will repay thee’. (Catechism of Trent, no. 4000)

Neither prayer nor any other virtuous act is meritorious without sanctifying grace. And yet even that prayer which impetrates sanctifying grace proceeds from some grace, as from a gratuitous gift, since the very act of praying is ‘a gift of God,’ as Augustine states (De Persever. 23) (Saint Thomas Aquinas. II-II, q. 83, a. 15)

In giving us his Son, his only Word (for he possesses no other), he spoke everything to us at once in this sole Word — and he has no more to say. . . because what he spoke before to the prophets in parts, he has now spoken all at once by giving us the All Who is His Son. Any person questioning God or desiring some vision or revelation would be guilty not only of foolish behaviour but also of offending him, by not fixing his eyes entirely upon Christ and by living with the desire for some other novelty (Saint John of the Cross. The Ascent of Mount Carmel 2, 22, 3-5). (Catechism of the Catholic Church, no. 65)

The Christian dispensation, therefore, as the new and definitive covenant, will never pass away and we now await no further new public revelation before the glorious manifestation of our Lord Jesus Christ (see 1Tim 6:14 and Tit 2:13). (Vatican Council II. Dogmatic constitution Dei Verbum, no. 4, November 18, 1965)

And so down to the time of Heraclius they were very great idolaters. From that time to the present a false prophet named Mohammed has appeared in their midst. This man, after having chanced upon the Old and New Testaments and likewise, it seems, having conversed with an Arian monk, devised his own heresy. […] He says that there is one God, creator of all things, who has neither been begotten nor has begotten. He says that the Christ is the Word of God and His Spirit, but a creature and a servant, and that He was begotten, without seed, of Mary the sister of Moses and Aaron. For, he says, the Word and God and the Spirit entered into Mary and she brought forth Jesus, who was a prophet and servant of God. And he says that the Jews wanted to crucify Him in violation of the law, and that they seized His shadow and crucified this. But the Christ Himself was not crucified, he says, nor did He die, for God out of His love for Him took Him to Himself into heaven. And he says this, that when the Christ had ascended into heaven God asked Him: Jesus, didst thou say: ‘I am the Son of God and God?’ And Jesus, he says, answered: ‘Be merciful to me, Lord. Thou knowest that I did not say this and that I did not scorn to be thy servant. But sinful men have written that I made this statement, and they have lied about me and have fallen into error.’ And God answered and said to Him: ‘I know that thou didst not say this word.’ There are many other extraordinary and quite ridiculous things in this book which he boasts was sent down to him from God. (Saint John Damascene. On heresies, no. PG 94, 766)

Nor do divine pronouncements on the part of preceding prophets offer him [Mohammed] any witness. On the contrary, he perverts almost all the testimonies of the Old and New Testaments by making them into fabrications of his own, as can be. seen by anyone who examines his law. It was, therefore, a shrewd decision on his part to forbid his followers to read the Old and New Testaments, lest these books convict him of falsity. It is thus clear that those who place any faith in his words believe foolishly. (Saint Thomas Aquinas. Summa Contra Gentiles, Book I, ch. 6)

[Against those denying natural theology]. If anyone shall have said that the one true God, our Creator and our Lord, cannot be known with certitude by those things which have been made, by the natural light of human reason: let him be anathema. (Denzinger-Hünermann 3026. Vatican Council I, Session III, Dogmatic constitution concerning the Catholic Faith, April 24, 1870)

Because God creates through wisdom, his creation is ordered: ‘You have arranged all things by measure and number and weight.’ (cf. Wis 11:20.) The universe, created in and by the eternal Word, the ‘image of the invisible God’, is destined for and addressed to man, himself created in the ‘image of God’ and called to a personal relationship with God (cf. Col 1:15, Gen 1:26). Our human understanding, which shares in the light of the divine intellect, can understand what God tells us by means of his creation, though not without great effort and only in a spirit of humility and respect before the Creator and his work (cf. Job 42:3). (Catechism of the Catholic Church, no. 299)

For they search busily among his works, but are distracted by what they see, because the things seen are fair. But again, not even these are pardonable. For if they so far succeeded in knowledge that they could speculate about the world, how did they not more quickly find its Lord? (Wis 13:7-9)

For what can be known about God is evident to them, because God made it evident to them. Ever since the creation of the world, his invisible attributes of eternal power and divinity have been able to be understood and perceived in what he has made. (Rom 1: 19-20)

Why do we call God the Father?
We call God the Father because by nature He is the Father of the Second Person of the Blessed Trinity, that is to say, of the Son begotten of Him; because God is the Father of all men, whom He has created and whom He preserves and governs; finally, because by grace He is the Father of all good Christians, who are hence called the adopted sons of God. (Catechism of Saint Pius X, no. 3, The first article of the Creed)

And so we learn that the true name of God is Father! The name which is beyond all other names: Abba! (cf. Gal 4:6). And in Jesus we learn that our true name is son, daughter! We learn that the God of the Exodus and the Covenant sets his people free because they are his sons and daughters, created not for slavery but for ‘the glorious liberty of the children of God’ (Rom 8:21). (John Paul II. Homily, no. 4, February 26, 2000)

Justice and mercy appear in the punishment of the just in this world, since by afflictions lesser faults are cleansed in them, and they are the more raised up from earthly affections to God. As to this Gregory says (Moral. 26, 9): ‘The evils that press on us in this world force us to go to God.’ (Saint Thomas Aquinas. Summa Theologica, I, q. 21, a. 4, ad. 3)

Faith gives us the certainty that God would not permit evil if he did not cause a good to come from that very evil. This was realized in a wondrous way by God in the death and resurrection of Christ. In fact, from the greatest of all moral evils (the murder of his Son) he has brought forth the greatest of all goods (the glorification of Christ and our redemption). (Compendium of the Catechism of the Catholic Church, no. 58)

A priest of the Society of Jesus, who during life devoted a great deal of time to the conversion of sinners, died with joy and confidence of salvation; this some considered to be excessive. Hence he was told that at death we should entertain sentiments of fear as well as of confidence. He answered: Have I served Mahomet? I have served a God who is so grateful and faithful; why, then, should I fear? (Saint Alphonsus Liguori. Dignity and duties of the priest: or, Selva, pg. 172)

‘O eternal God, you know what is hidden and are aware of all things before they come to be: you know that they have testified falsely against me. Here I am about to die, though I have done none of the things with which these wicked men have charged me.’ The Lord heard her prayer. […] They rose up against the two elders, for by their own words Daniel had convicted them of perjury. According to the law of Moses, they inflicted on them the penalty they had plotted to impose on their neighbor: they put them to death. Thus was innocent blood spared that day. (Dan 13:42-44.61-62)

Blessed are you, and praiseworthy, O Lord, the God of our fathers, and glorious forever is your name. For you are just in all you have done; all your deeds are faultless, all your ways right, and all your judgments proper. You have executed proper judgments in all that you have brought upon us and upon Jerusalem, the holy city of our fathers. By a proper judgment you have done all this because of our sins. (Dan 3:26-28)

The point is clear in the case of Mohammad. He seduced the people by promises of carnal pleasure to which the concupiscence of the flesh goads us. His teaching also contained precepts that were in conformity with his promises, and he gave free rein to carnal pleasure. (Saint Thomas Aquinas. Summa contra Gentiles, Book 1, ch. 6)

The Mahometan Paradise, however, is only fit for beasts; for filthy sensual pleasure is all the believer has to expect there. (Saint Alphonsus Liguori. The History of Heresies and their Refutations, no.2, p. 93)

At the resurrection they neither marry nor are given in marriage but are like the angels in heaven. (Mt 22:30)

Be sure of this, that no immoral or impure or greedy person, that is, an idolater, has any inheritance in the kingdom of Christ and of God. Let no one deceive you with empty arguments, for because of these things the wrath of God is coming upon the disobedient. (Eph 5: 5-7)

Rightly is this blessedness promised to purity of heart. For the brightness of the true light will not be able to be seen by the unclean sight: and that which will be happiness to minds that are bright and clean, will be a punishment to those that are stained. (Leo I the Great. Sermon XCV, A Homily on the Beatitudes, no. VIII)

Thus, a double error is set aside by the foregoing points. There is the mistake of those who believe that all things follow, without any rational plan, from God’s pure will. This is the error of the exponents of the Law of the Moors, as Rabbi Moses says; according to them, it makes no difference whether fire heats or cools, unless God wills it so. (Saint Thomas Aquinas. Summa contra Gentiles. Book III, ch. 97)

Because God creates through wisdom, his creation is ordered: ‘You have arranged all things by measure and number and weight’ (Wis 11:20). The universe, created in and by the eternal Word, the ‘image of the invisible God’, is destined for and addressed to man, himself created in the ‘image of God’ and called to a personal relationship with God (Gen 1:26) […] from God’s goodness, it shares in that goodness – ‘and God saw that it was good. . . very good’ (Gen 1:4, 10, 12, 18, 21, 31). (Catechism of the Catholic Church, no. 299)

This is good and pleasing to God our savior, who wills everyone to be saved and to come to knowledge of the truth. (1Tim 2: 3-4)

At the dawn of the new Millennium, we wish to propose once more the message of hope which comes from the stable of Bethlehem: God loves all men and women on earth and gives them the hope of a new era, an era of peace. His love, fully revealed in the Incarnate Son, is the foundation of universal peace. When welcomed in the depths of the human heart, this love reconciles people with God and with themselves, renews human relationships and stirs that desire for brotherhood capable of banishing the temptation of violence and war. (John Paul II. World Day of Peace, no. 1, January 1, 2000)