I have a copy of Denzinger's "The Sources of Catholic Dogma." It is the translation of the Thirteenth Edition by Roy J. Deferrari in 1955. This is one of the dogmatic sources I have occasion to turn to as the basis of what I believe. I say "one of" since there also exists far more complete texts of many important documents in which the Church has expressed Her doctrinal and dogmatic positions and teachings.
I certainly do recommend that Catholics who desire to be informed authoritatively regarding their faith purchase a copy of Denzinger and spend time reading it. Indeed, I equally recommend the other dogmatic sources of Catholic teaching, the Catechism of the Council of Trent, the Canons and Decrees of the Council of Trent, Dogmatic Canons and Decrees of Trent and Vatican I, The Church Teaches, the Fundamentals of Catholic Dogma, Moral Theology, Moral Theology (by Heribert Jone), the Bible (Douay-Rheims, Haydock version is best), all the many numerous Papal encyclicals, writings of the Ancient Church Fathers and so forth.
But what I often find is that people tend to be unwilling to take the time for these books and classics. All too many would prefer to read such contemporary volumes as those written by traditional Catholics (e. g. We Resist You to the Face, the Great Fašade, Open Letter to Confused Catholics, and even my own book, The Resurrection of the Roman Catholic Church). Somehow it seems easier to read these modern (though sound) books instead of the classical sources of our beliefs in their most authoritative forms.
I realize that a big part of this stems from an understandable and almost quaint and charming humility on our part. We tend to feel that the reading of such classics and solid food books is way above ourselves, something that only the very learned people should ever do, not us ordinary non-theologically-trained peons. But before we smugly congratulate ourselves on our "quaint and charming humility" I think it bears mentioning that another component of our near avoidance of such volumes may be a fear that such books, being so far above our own humble level of comprehension, might be, or at least seem, quite boring, technical, and pedantic.
Who has the patience to plow though reams and reams of pedantic scholastic references with continual citations of obscure authors in multitudinous languages with which we are familiar, to say nothing of linguistic, historical, allegorical, and other references with which we are completely unfamiliar? Far easier it would seem to just pick up some modern book, written by a layman like us, at our level, and no doubt all the more directly addressing our present situation. After all, those ancients had their problems, not ours. What use can understanding theirs be in understanding ours?
I come to tell you that this is not the way it is with these crucial sources at all. If Denzinger's Enchiridion (or many of the others) seems large and intimidating, then instead choose a Papal encyclical. Pope Pius XI's Mortalium Animos for example is short and sweet and to-the-point. I think you will be astonished to see just how easy it is to understand what the Pope is saying, and of course since you can know for a fact that you are hearing the Voice of Peter speaking in it, you don't have to wonder about it at all, testing it, judging it, weighing it and so forth as proves necessary with postconciliar documents, and for that matter, any contemporary book.
By the end, you will be wishing for more, and of course, more there indeed is, very much more. In my book, one of the objects of an Appendix entitled "The Pope Condemns Vatican II" is to share with the reader my appreciation of these dogmatic sources, particularly the papal pronouncements, but also a few other similarly authentic and authoritative sources of our beliefs. It is not enough to cite a number of specific points that prove the Vatican II religion to be one that has been Papally condemned. All too often, traditional Catholics take the easy way out and only read the modern books, only to find any and all manner of limitations in them when it comes to the time of testing. With no rooting in the dogmatic sources of our Faith, why not go along with the modern Vatican direction(s) when the going gets rough?
As given in my book, the extracts given not only prove the points intended, but are deliberately large and extended enough to show a glimpse of what more there is in the way of spiritual riches to be contained in the authoritative sources provided by the Church. Just as the traditional Latin Mass provides the fullness of the Graces intended by Christ through His Church, the traditional teachings by the Popes down through history provide a solid grounding in our Faith, one that cannot be shaken by onslaughts of the Modernists and their countless minions. And most important to note, they are NOT hard to read.
Or perhaps we fear they may call us to a higher standard than we are willing to live, and with no room for doubt as to their authoritativeness. Would we really be willing to continue wandering in confusion and squandering the precious life that God has given us in fruitless and misdirected attempts to "be good" in our own power, by our own limited and fallen lights? How easy to think to ourselves that we are not responsible for what we do not know. Yet that very position is to accept something of a Purgatorial sentence. To be worthy of Heaven we will be held to all of it. We can learn it now when it is easy or in Purgatory when it is hard.
The choice is ours, but one of the pains of Purgatory will be seeing what we could have accomplished for God had we sought, rather than avoided, the whole counsel of God and carried it out. Relatives and friends who might have been brought from damnation to salvation, people we might have blessed in ways they truly needed (and God intended for them, had only we made ourselves willing participants of God's will). We must hunger for the Word, not to fill our head with knowledge that puffs up nor with rules to bind and complicate our lives, but to instill in us that outlook that sees things the way God sees them, and become imbued with the Mind of the Church.
Take what we already know and we can build on it logically to some extent, but human logic can prove fallible and what better check for it than to see what the Church teaches in these more advanced and subtle points which we are bound to come across sooner or later in our reading of these dogmatic sources. I cannot recommend them highly enough, they are so important, and provide such a solid basis. Indeed, as our minds are more and more conformed to the image of Christ, we will more and more find our thinking actually vindicated by these sources, a wonderful and awesome experience.
Which brings me to Denzinger in particular. As you can see from above, I can recommend it without reservation to anyone serious about learning their Faith in all its details as dogmatically established in the prime sources. This does not mean that there cannot be excesses even with the use and reading of such truly commendable reading as I have advocated so far. Of course, Catholics of most past generations did not have Denzinger on their shelves as we often do, but neither did they need it. And further back, when most of what it contains was as yet unwritten, the average Catholic had something far superior, and that was the living memory of what the ancient Church had been, as was still being documented by the Ancient Church Fathers. But now we do have this luxury of having so many authoritative sources of dogma and doctrine at our fingertips.
More than once I have seen traditional Catholics who can quote Denzinger chapter and verse like a Protestant quotes the Bible. And often this entails some of the same manners of misquoting it or misapplying it as the Protestants have misquoted or misapplied the Bible. I see this as the result, not of reading such books too much, but of reading them too little.
The more familiar we are with the authoritative sources of our beliefs, (and not just the parts that support our current particular claims, but the general run of what the documents say in their entirety) the more able we become to weigh the intent and meaning of each thing said. This also means that we will have read the balancing statements that put declarations into context, showing that some declarations that might sound absolute in isolation might in fact be governed by other extenuating circumstances. One finds for example a number of seeming flat-out condemnations of usury, and often in terms that make it sound as if any interest for any loan constitutes usury. Are we to conclude therefore that a person who goes to the bank and opens up a savings account that pays a nominal interest rate on the monies contained therein has incurred the sin of usury? Yet when we are familiar with it all, we find that Pope Gregory IX wrote that "He who loans a sum of money to one sailing or going to market, since he has assumed upon himself a risk, is not to be considered a usurer who will receive something beyond his lot." (Denzinger 448) But without that balance, one could reach an erroneous conclusion.
Far more obvious errors can result from one's lack of familiarity with a particular source, be it Denzinger's as a volume, or any of the Popes and Councils quoted therein. Indeed, in the days before I read Denzinger, I had such an experience that shows just how necessary it is that one at least read an entire citation as given rather than just a mere sentence or quotation contained therein.
A correspondent, also a contributor to The Daily Catholic, once asked me "I first want to ask you what you, as a sedevacantist, have to say about the teaching of the Council of Constance, Denzinger 646?" Looking up Denzinger 646, one finds the following: "If the pope is wicked and especially if he is foreknown, then as Judas, the Apostle, he is of the devil, a thief, and a son of perdition, and he is not the head of the holy militant Church, since he is not a member of it." Needless to say, that struck me as rather strong, and indeed I was wondering why it was that no sedevacantist seemed to be pointing to it.
But something bothered me about that quote. It didn't speak of a pope teaching known and papally condemned religious error(s), but merely of his being wicked. Given the presence of some wicked popes over the Church's history, it seemed to me to be a bit much to claim that mere wickedness could be enough to remove him from that office.
So I responded,
"At first it seems a little strong, but perhaps by 'wicked' in such a context they are not referring to the man's own possible lack of moral character personally, but about one who wickedly poses a spiritual danger to the Church. That would be my guess."
Again, this struck me as being odd, just a bit too "hair-trigger" about removing a pope. Despite my sedevacantist opinion, I was astonished and horrified that the Church could have ever taught such a thing.
Imagine the surprise and joy some several days later when I finally stumbled upon the answer to that tiny mystery. My later response to him once I figured out what had happened was
"Sorry, I misread the text. When I looked it up I only saw the part about how a wicked pope is supposedly not a pope at all, and I was astonished that the Church could teach such a thing, but if there it was, then there it was. What I didn't see (and didn't realize) was what was brought out in the short letter to the Remnant where you gave it in full context (the remainder of which is some two pages previous, and it states 'It is an ERROR to teach that...' So now it makes a lot more sense!
"I should have known better as I had already been through this with Denzinger before. I once opened it to some random spot and found all the most bizarre and extraordinary teachings about the Eucharist, that it ceases to be the Body of Christ if chewed, or when swallowed, etc., and for the better part of an hour I racked my brain and scratched my head and furrowed my brow trying to figure out how the Church could have ever taught such nonsense, and I was watching my entire understanding of Sacramental theology melting away right before my eyes. Then I found the place (on the previous page) where it said 'The following propositions are condemned:' Ah! Whew! So those statements were just nonsense after all, as I suspected. Still, it sure felt weird trying to reconcile such nonsense with the Catholic teaching I already knew.
"That is why I interpreted the statement as given in the most orthodox sense I could give it, namely that by 'wicked' it could only (if it had been doctrine and not some condemned proposition) mean nefariously and notoriously heretical. Unfortunately today, many things in the Vatican II documents and later documents require such 'interpretation' in order to be reconciled with Catholic teaching at all. I wonder if some of the mistaken notions taught in such recent documents actually came from people making the same mistake as I did in reading the older documents. If Ratzinger can admit that Gaudium et Spes is a 'counter-syllabus' then perhaps there is room to believe that its preparers had simply read the Syllabus of Errors as doctrine and not as the condemned propositions it actually consists of, and then the Council Fathers did their level best to 'interpret' such heresies in some sense at least remotely in line with the [teaching of the] Church."
Obviously, the first lesson one gains from this is that one must read a statement in context, in the case of Denzinger, at least the context of the full citation as given, and not merely the numbered text pointed to. Perhaps the fact that no sedevacantist has ever even mistakenly used that text is that none of them ever looked through Denzinger for "proof-texts" with which to prove something. Looking for such a thing is what most often leads to mistaken readings of the text and some occasionally horrible misquotations and misapplications of perfectly valid and authoritative texts.
But a careful reading of each text in full, and even better, a great deal of authoritative sources at length, seeking to learn what they have to say instead of merely looking for some specific thing one is looking for, is what best and most of all prevents such mistakes from happening. Again, this is best solved by lots of reading of the authoritative sources and becoming familiar with them. Most of all, one must become familiar with the overall mode of thought that pervades all such documents and allows one to understand best what is meant by each.
I maintain however, that where I have quoted the authoritative sources in the above-mentioned Appendix of my book, the remainder of the sources (not given therein) only augments the point I seek to make from the extracts I give, for so indeed I found by reading them at length. As for my correspondent, my final paragraphs summed up my real answer to the question he raised:
"So, let me start again on this text: Clearly, this is talking about 'wicked' as in evil personally (such as Pope Alexander VI), whom the Church has always acknowledged as a pope despite his [widely acknowledged] wickedness. However, the sedevacantist 'issue' is not about any possible 'wickedness' on the part of the Vatican leadership, but evident doctrinal error. Else St. Bellarmine and others could not have even speculated about the prospect of a pope ceasing to be pope due to doctrinal error if 'wickedness' encompassed such a problem; the question would have been quite moot to such doctors, theologians, and canonists, given this condemnation."
So yes, there can be pitfalls and risks. But by and large, one can only strengthen one's spiritual position and standing by familiarizing oneself with the great and authoritative teachings of the Church as given in Her most authoritative sources.