As many know, I am a former Roman Catholic, and unlike many ex-Catholics, I am well-read in official Catholic dogmatic theology and history (e.g., I have an extensive Catholic library, such as the works of Aquinas, Bellarmine, the Ecumenical Councils, and modern apologetic works). I also spent a number of years studying theology at a top Catholic theological institution (Maynooth). In light of this, it is apropos to make this post wherein I will explain why I am not a Catholic, why I will never return to Catholicism, and why, if you are considering joining Catholicism (or have joined), you should reconsider.
As an important prelude, do note the following: Rome makes a number of claims which can be
tested. Contrary to the attitude of many, Rome is not the "default" church/position. First and foremost, her de fide dogmas are (or, at the very least, must be), according to her very own claims, apostolic in origin. While
there is an allowance for some development (e.g., greater appreciation of a
belief; development/refinement of terminology, etc), the “substance” of the dogma
must be apostolic in origin (i.e., taught by Jesus or, through the Holy Spirit,
revealed to the Apostles before the closing of the Deposit of Faith). Note the
following from Catholic sources.
783 [DS 1501] The sacred and holy ecumenical and general Synod of Trent, lawfully assembled in the Holy Spirit, with the same three Legates of the Apostolic See presiding over it, keeping this constantly in view, that with the abolishing of errors, the purity itself of the Gospel is preserved in the Church, which promised before through the Prophets in the Holy Scriptures our Lord Jesus Christ the Son of God first promulgated with His own mouth, and then commanded “to be preached” by His apostles “to every creature” as the source of every saving truth and of instruction in morals [Matt. 28:19 ff.; Mark 16:15], and [the Synod] clearly perceiving that this truth and instruction are contained in the written books and in the unwritten traditions, which have been received by the apostles from the mouth of Christ Himself, or from the apostles themselves, at the dictation of the Holy Spirit, have come down even to us, transmitted as it were from hand to hand, [the Synod] following the examples of the orthodox Fathers, receives and holds in veneration with an equal affection of piety and reverence all the books both of the Old and of the New Testament, since one God is the author of both, and also the traditions themselves, those that appertain both to faith and to morals, as having been dictated either by Christ’s own word of mouth, or by the Holy Spirit, and preserved in the Catholic Church by a continuous succession. And so that no doubt may arise in anyone’s mind as to which are the books that are accepted by this Synod, it has decreed that a list of the Sacred books be added to this decree.
Also note the following from the Vatican I's dogmatic constitution on the Church which defined papal infallibility, Pastor Aeternus:
[DS 3070] For, the Holy Spirit was not promised to the successors of Peter that by His revelation they might disclose new doctrine, but that by His help they might guard sacredly the revelation transmitted through the apostles and the deposit of faith, and might faithfully set it forth. Indeed, all the venerable fathers have embraced their apostolic doctrine, and the holy orthodox Doctors have venerated and followed it, knowing full well that the See of St. Peter always remains unimpaired by any error, according to the divine promise of our Lord the Savior made to the chief of His disciples: “I have prayed for thee, that thy faith fail not: and thou, being once converted, confirm thy brethren” [Luke 22:32].
We can see this in the dogma of the Immaculate Conception. Pius IX, in defining it as a de fide dogma Ineffabilis Deus, asserted that:
[The doctrine of the Immaculate Conception] always existed in the Church as a doctrine that has been received from our ancestors, and that has been stamped with the character of revealed doctrine"
Against the evolution of doctrine (and as a result, the naïve and ignorant belief that “tradition” can reveal new doctrines, etc), consider the following from Pius X (a canonised saint) in his September 1907 encyclical against Modernism, Pascendi Dominici Gregis:
The Evolution of Doctrine
26. To finish with this whole question of faith and its shoots, it remains to be seen, Venerable Brethren, what the Modernists have to say about their development. First of all they lay down the general principle that in a living religion everything is subject to change, and must change, and in this way they pass to what may be said to be, among the chief of their doctrines, that of Evolution. To the laws of evolution everything is subject - dogma, Church, worship, the Books we revere as sacred, even faith itself, and the penalty of disobedience is death. The enunciation of this principle will not astonish anybody who bears in mind what the Modernists have had to say about each of these subjects. Having laid down this law of evolution, the Modernists themselves teach us how it works out. And first with regard to faith. The primitive form of faith, they tell us, was rudimentary and common to all men alike, for it had its origin in human nature and human life. Vital evolution brought with it progress, not by the accretion of new and purely adventitious forms from without, but by an increasing penetration of the religious sentiment in the conscience. This progress was of two kinds: negative, by the elimination of all foreign elements, such, for example, as the sentiment of family or nationality; and positive by the intellectual and moral refining of man, by means of which the idea was enlarged and enlightened while the religious sentiment became more elevated and more intense. For the progress of faith no other causes are to be assigned than those which are adduced to explain its origin. But to them must be added those religious geniuses whom we call prophets, and of whom Christ was the greatest; both because in their lives and their words there was something mysterious which faith attributed to the divinity, and because it fell to their lot to have new and original experiences fully in harmony with the needs of their time. The progress of dogma is due chiefly to the obstacles which faith has to surmount, to the enemies it has to vanquish, to the contradictions it has to repel. Add to this a perpetual striving to penetrate ever more profoundly its own mysteries. Thus, to omit other examples, has it happened in the case of Christ: in Him that divine something which faith admitted in Him expanded in such a way that He was at last held to be God. The chief stimulus of evolution in the domain of worship consists in the need of adapting itself to the uses and customs of peoples, as well as the need of availing itself of the value which certain acts have acquired by long usage. Finally, evolution in the Church itself is fed by the need of accommodating itself to historical conditions and of harmonising itself with existing forms of society. Such is religious evolution in detail. And here, before proceeding further, we would have you note well this whole theory of necessities and needs, for it is at the root of the entire system of the Modernists, and it is upon it that they will erect that famous method of theirs called the historical.
27. Still continuing the consideration of the evolution of doctrine, it is to be noted that Evolution is due no doubt to those stimulants styled needs, but, if left to their action alone, it would run a great risk of bursting the bounds of tradition, and thus, turned aside from its primitive vital principle, would lead to ruin instead of progress. Hence, studying more closely the ideas of the Modernists, evolution is described as resulting from the conflict of two forces, one of them tending towards progress, the other towards conservation. The conserving force in the Church is tradition, and tradition is represented by religious authority, and this both by right and in fact; for by right it is in the very nature of authority to protect tradition, and, in fact, for authority, raised as it is above the contingencies of life, feels hardly, or not at all, the spurs of progress. The progressive force, on the contrary, which responds to the inner needs lies in the individual consciences and ferments there - especially in such of them as are in most intimate contact with life. Note here, Venerable Brethren, the appearance already of that most pernicious doctrine which would make of the laity a factor of progress in the Church. Now it is by a species of compromise between the forces of conservation and of progress, that is to say between authority and individual consciences, that changes and advances take place. The individual consciences of some of them act on the collective conscience, which brings pressure to bear on the depositaries of authority, until the latter consent to a compromise, and, the pact being made, authority sees to its maintenance.
With all this in mind, one understands how it is that the Modernists express astonishment when they are reprimanded or punished. What is imputed to them as a fault they regard as a sacred duty. Being in intimate contact with consciences they know better than anybody else, and certainly better than the ecclesiastical authority, what needs exist - nay, they embody them, so to speak, in themselves. Having a voice and a pen they use both publicly, for this is their duty. Let authority rebuke them as much as it pleases - they have their own conscience on their side and an intimate experience which tells them with certainty that what they deserve is not blame but praise. Then they reflect that, after all there is no progress without a battle and no battle without its victim, and victims they are willing to be like the prophets and Christ Himself. They have no bitterness in their hearts against the authority which uses them roughly, for after all it is only doing its duty as authority. Their sole grief is that it remains deaf to their warnings, because delay multiplies the obstacles which impede the progress of souls, but the hour will most surely come when there will be no further chance for tergiversation, for if the laws of evolution may be checked for a while, they cannot be ultimately destroyed. And so they go their way, reprimands and condemnations notwithstanding, masking an incredible audacity under a mock semblance of humility. While they make a show of bowing their heads, their hands and minds are more intent than ever on carrying out their purposes. And this policy they follow willingly and wittingly, both because it is part of their system that authority is to be stimulated but not dethroned, and because it is necessary for them to remain within the ranks of the Church in order that they may gradually transform the collective conscience - thus unconsciously avowing that the common conscience is not with them, and that they have no right to claim to be its interpreters.
28. Thus then, Venerable Brethren, for the Modernists, both as authors and propagandists, there is to be nothing stable, nothing immutable in the Church. Nor indeed are they without precursors in their doctrines, for it was of these that Our Predecessor Pius IX wrote: These enemies of divine revelation extol human progress to the skies, and with rash and sacrilegious daring would have it introduced into the Catholic religion as if this religion were not the work of God but of man, or some kind of philosophical discovery susceptible of perfection by human efforts. On the subject of revelation and dogma in particular, the doctrine of the Modernists offers nothing new - we find it condemned in the Syllabus of Pius IX., where it is enunciated in these terms: Divine revelation is imperfect, and therefore subject to continual and indefinite progress, corresponding with the progress of human reason; and condemned still more solemnly in the Vatican Council: The doctrine of the faith which God has revealed has not been proposed to human intelligences to be perfected by them as if it were a philosophical system, but as a divine deposit entrusted to the Spouse of Christ to be faithfully guarded and infallibly interpreted. Hence the sense, too, of the sacred dogmas is that which our Holy Mother the Church has once declared, nor is this sense ever to be abandoned on plea or pretext of a more profound comprehension of the truth. Nor is the development of our knowledge, even concerning the faith, impeded by this pronouncement - on the contrary it is aided and promoted. For the same Council continues: Let intelligence and science and wisdom, therefore, increase and progress abundantly and vigorously in individuals and in the mass, in the believer and in the whole Church, throughout the ages and the centuries - but only in its own kind, that is, according to the same dogma, the same sense, the same acceptation.
I open with this, as (1) the development of doctrine argument (cf. Newman's 1845 thesis) has been abused by many Catholic apologists and (2) if Rome is wrong about one dogma, she is, by her own standards, a false Church)--it is all-or-nothing.
So, in no particular order, the top reasons why I believe Roman Catholicism to be a false gospel, under the anathema of Gal 1:6-9:
The Veneration of Images (as defined at 2 Nicea, and re-iterated at Trent and other sources) is (1) refuted by the earliest centuries of Christian commentators and (2) is idolatrous
For more, see the listing of articles at: Answering Fundamentalist Protestants and Roman Catholic/Eastern Orthodox on Images/Icons
For a presentation of official Roman Catholic teachings on this topic (something modern Roman Catholic apologists are often not forthright about), see Douglas Beaumont and the Real Issues About the Catholic (and Eastern Orthodox) Teachings on the Veneration of Icons/Images
For a youtube presentation on the unanimous patristic testimony against, not just veneration of images but the presuppositions thereof which are part-and-parcel of the Catholic (and Eastern Orthodox) dogma, see:
A Case Against the Veneration of Images
Roman Catholic Mariology is ahistorical and absent (often contradicted) by Early Christian Writings
On the Immaculate Conception: Answering Tim Staples on Patristic Mariology and the Immaculate Conception
On the Bodily Assumption: Refuting Taylor Marshall on the Bodily Assumption of Mary
On Mariology itself (e.g., purported biblical evidence for the Immaculate Conception; the perpetual virginity), see:
Behold the Mother of My Lord: Towards a Mormon Mariology
The Catholic Mass is not a sacrifice which propitiates (appeases) God's Wrath Against Sin and Transubstantiation (not "Real Presence," per se) Rests on Eisegesis of the Bible and Patristics
For a fuller discussion, including some technical issues from Greek (e.g., the meaning of αναμνησις), see the listing of articles at:
Responses to Robert Sungenis, Not by Bread Alone (2000/2009)
The Vatican I (1870) Dogma of the Papacy and the Nature of Petrine Supremacy is Opposed to History
For an explication of the de fide dogma, see:
Pius IX, Pastor Aeternus (Vatican Council I [1870])
Edward Denny, Papalism: A Treatise on the Claims of the Papacy as Set Forth in the Encyclical Satis Cognitum (1912)
George Salmon, The Infallibility of the Church (1888)
A. Edward Siecienski, The Papacy and the Orthodox: Sources and History of a Debate (cf. Edward Siecienski on The Church of Rome and the Quartodeciman Controversy)
Paul Pavao, Rome's Audacious Claim: Should EveryChristian Be Subject to the Pope? (Selmer, Tenn.: Greatest Stories Ever Told, 2019)
On 1 Clement, a commonly-cited and abused text by Roman apologists, see:
Cyril Richardson on the occasion of 1 Clement
A Triad of Early Christians Against the Trinity Being an Apostolic Belief (Justin, Origen, and Tertullian)
C.J. Labuschagne on the language of "incomparability" in the Old Testament and Literature of Surrounding Cultures and
Refuting Jeff Durbin on "Mormonism" on the "number" of God
Lynn Wilder vs. Latter-day Saint (and Biblical) Theology on Divine Embodiment
Blake T. Ostler, Out of Nothing: A History of Creation ex Nihilo in Early Christian Thought
Daniel O. McClellan, James Patrick Holding refuted on Creation Ex Nihilo
