Welcome back and Happy Easter*
First off, I would simply say that while I second the need to read
The Summa Theologiae, it acts as more of an encyclopedia index of sorts. Because of Thomas's massive broad overview in all things
The Summa is essentially an index and was intended to be an instructional guide for theology students, including seminarians and the literate laity at the time. I highly encourage you use it as one of (if not your main) reference source. It's an invaluable gift and treasure of the Church. With that being said you kind of have to know where St. Thomas was coming from when he wrote it and the philosophical backbone behind it. In other words what did he build it off of and why? Well, it was a response to Aristotle's secular works becoming increasingly popular, and so what we find in
The Summa is essentially Aristotelian natural law & ethics complimented with the Catholic Churches understanding of the world. In short, St. Thomas took natural law and supernatural law and combined them. Regardless this comes with the huge task of understanding Aristotle if you are to make complete sense of Aquinas. The beauty of
The Summa overall is it shows the harmony of natural law with the theological; it shows how the two are not disconnected but naturally work together and are complimentary.
As far as Catholic writing's go there's volumes upon volumes, it just depends on where you want to start and what you're researching or wish to understand. I mean this literally, there's an entire library devoted in the Vatican; the Vatican Apostolic Library, [...] It has 75,000 codices from throughout history, as well as 1.1 million printed books, which include some 8,500 incunabula (a book, pamphlet). So, you're talking about a massive treasury of information. It's easy to get lost in the weeds of all of this, but I would add, having some clear indication of what and why you're studying is valuable.
A good way I've found to discover new resources is simply to research the works of the Saint of that day (find the Saint of the day here -
https://catholicsaints.info), you'll be pleasantly surprised and glad you did. Because today is Easter and the Feast of Isidore of Seville (4/4), one of my personal favorites and Catholic or otherwise should read his Etymologiae (The Etymologies).
The Etymologies summarized and organized a wealth of knowledge from hundreds of classical sources; three of its books are derived largely from Pliny the Elder's
Natural History.
At the moment I can't find a link for the book online though I've found one in the past, so if you simply search "Isidore of Seville The Etymologies pdf" you mightbe able to find a copy. If you're naturally fond of these sorts of texts I would simply buy it.
Generally Catholics have theological and supernatural basics on their side which supports and grounds most of their common sense logic but sometimes they lack the natural law philosophical implications for what they believe, which is I would suspect, why St. Thomas is so perennial and always in vogue. And so as a rule of thumb knowing the Bible (it's history, the main people, themes, allegory's, etc.) should probably come "first" or at very least be something you're constantly referencing back too with whatever studies you're interested in. "Philosophy" itself can become baseless and empty quite quickly if you have no religious backbone attached to you. So it's a bit of both worlds, you need to have an understanding of natural philosophical law + theological law at the same time, but not to get overly distracted with natural philosophical law, because again, it can quickly distort and undermine everything in the theological realm.
"See to it that no one makes a prey of you by philosophy and empty deceit, according to human tradition, according to the elemental spirits of the universe, and not according to Christ." - Colossians 2:8
It's easy to get carried away with secular philosophy, so don't get carried away. With that being said examine whatever you are examining with prudence and good discernment.
All in all there's a plethora of different avenues one can take to find excellent Catholic resources and information is not lacking by any stretch of the imagination. As I mentioned having a grounding in ancient philosophy can be very beneficial, especially when trying to understand St. Augustine and St. Thomas. Realize that these theologians were building upon natural philosophical laws which scholastically and historically were the norm. And so, to truly appreciate St. Augustine or St. Thomas one may find it fruitful to delve into Plato and Aristotle. Yet, again I do caution with being led astray by weak empty secular philosophy and so one must use sound judgment and reference back to the master Catholic teachers when doing so. In other words you'll probably come to the wrong understanding of scripture (as many early philosophers did and still do) if you aren't referencing the Saints first and foremost. The Saint is someone you can read who has been singled out by The LORD as not necessarily 'free from error', but someone of clear reasoning and mind who you can trust when reading them. In other words it's almost always a very safe bet to read the Saints and to accept what they say without needing to put them under a microscope. While the Saints do indeed differ on different topics from time to time, overall you can read them and you shouldn't fall into grave error(s).
So as to not write you a book in this thread, because the goal is to read actual good books, here's a brief outline ...
Resources:
Catholic Encyclopedia:
One of the biggest Catholic resources on the Internet, containing more than 10,000 articles
www.newadvent.org
The Fathers of the Church
Featuring the Church Fathers, Catholic Encyclopedia, Summa Theologica and more.
www.newadvent.org
As someone already referenced the The Catholic Encyclopedia is essential. With that being said it is vast and multi-faceted. If you don't have a basic understanding of philosophy it's not the resource you want to go to first because one could easily get lost in
links of connected topics. Because were talking about something which encompasses literally all of life and reality, one can quickly get sidetracked from the topic at hand potentially. This is simply a word of caution, because at first when seemingly 'all knowledge' is presented it is a great blessing in some regards, but at the same time, if there is no prudence involved in what you're studying you can potentially come to the incorrect assumptions. An example of this would be search 'Christmas'. It's a decent overview of the topic, but by no means has all of the essential information. What I mean by this is one shouldn't try to 'construct' their own beliefs around encyclopedia definitions, because again it is very broad and without prudence you're liable to serious error if you are attempting to understand
everything. It is simply an encyclopedia and should be treated as such.
CatholicSaints.Info
notes about your extended family in heaven
catholicsaints.info
CatholicSaints.Info is a solid reference which includes a plethora of other Saintly individuals you may have never heard of. I'm not entirely sure where he's getting his information from, so use your better judgement. For example not every Marian apparition on the site is approved by the Church, nor is from my understanding, every 'Saint' a 'Saint' on the site. I could be mistaken though. I believe he may be getting his Saint list from the
Acta Sanctorum (The Lives of the Saints) and or the The Bollandists. And so use your better judgement when going through that site, though it's one of the few I'm even aware of online with a broad array of obscure Saints, again, use your better judgement.
As far as Catholic authors, as mentioned there's an incredible array literally so you would have to be somewhat more specific as to what exactly you're looking for or even interested in. Modern Catholic Saints are invaluable and also worth mentioning, yet if the goal is to have a solid foundation for Catholic theology you have to back track a bit, if that's the goal.
In regards to secular philosophy in order to understand said Plato or Aristotle you have to go back to the beginning, which if I was giving you a timeline as to where "logic starts" and or what are "entry level" resources of secular philosophy which lead to Catholicism potentially and or help to assist us in understanding natural law, you have to start with Heraclitus and or the Stoics. It should be said though that doing so could quickly devolve into pantheism if you have no basic philosophical understanding of anything. Again, as mentioned earlier if you are Catholic normally the graces given assist the common sense in such an incredible way whereby most Catholics with no philosophical background can easily come to correct conclusions if they are practicing and in albeit in a
normal healthy mindset; in a presumed state of grace. With that being said I'm hesitant to simply start rattling off secular philosophers if you have no basic understanding of philosophy.
Catholic Theology and Apologetics as you've indicated requires knowing the foundational principles of philosophy. Knowing St. Thomas is wonderful, but of apologetic's is the goal knowing Aristotle is just as important. To know Aristotle you need to know Plato, to know Plato you need to know Socrates, to know Socrates you need to know the Stoics, to know the Stoics you need to know Heraclitus, etc. If you are up to the task, as mentioned if you study Biblical history and it's main prophets and timeline concurrently with the secular world's some major pieces of lifes puzzle will inevitably come your way. For example some claims are that Plato got his ideas from Moses. If this is true how would you know if you don't understand Plato? Must one understand
everything? No, yet one should have a solid understanding of what is being referenced if the intent is indeed apologetics, and so you're going to have to understand secular philosophy to some degree.
A decent (while no means perfect) beginning world history/philosophy book is
The Great Conversation: A Historical Introduction to Philosophy. Keep in mind though, the author has a slightly secular bent, yet he's using the 'basic' common understanding which most academic 'philosophers' understand on the topics which is why I mention the book. You're getting the secluar point of view on philosophy from the horses mouth without loads of propaganda. Overall its a decent overview chronologically and his bias is not in your face as many secular philosophy books can be. For the record though, you have to go back in time with these topics. The book almost attempts at a certain point to rewrite history, which is everywhere nowadays, so keep that in mind if you read this. It discusses much in regards to modern philosophy and humanistic ideas which are the antithesis to the scholastic period, so realize much of what the world calls 'philosophy' is in fact heretical and the complete opposite of the goal; which is to understand wisdom and truth correct?
Now in its fifth edition, this historically organized introductory text treats philosophy as a dramatic and continuous story--a conversat...
www.goodreads.com
If I were you, which I'm not, I would use this as a rough outline of secular works to build up the Catholic ones. Again, don't get carried away with the pantheism and sometimes overt pseudo spirituality in these, but if you feel grounded in the faith enough then use them as a foundation to understanding natural law. If youre advanced enough read them alongside
The Summa.
