According to Scripture, is the Catholic Church infallible?
In Scripture, we find the admonition
Titus 2:1 You, however, must teach what is appropriate to sound doctrine.
But, what is "sound doctrine"? Is sound doctrine only in Scripture? Is sound doctrine in Scripture and something else? If so, where?
Well, let's break down the question into it's smallest parts and see where the answer takes us.
Doctrine means Tradition
Doctrine means Teaching. Strangely enough, it also means Tradition. Yes, Tradition means Teaching. Let me show you.
2 Thessalonians 2:15 King James Bible (KJV) Therefore, brethren, stand fast, and hold the traditions which ye have been taught, whether by word, or our epistle.
2 Thessalonians 2:15 New International Version (NIV)
15 So then, brothers and sisters, stand firm and hold fast to the teachings we passed on to you, whether by word of mouth or by letter.
So, holding on to sound doctrine means to hold on to sound tradition.
Why do I make this point?
I make the point that "tradition" means teaching, and I make the point using two Protestant Bibles, because many of our separated brothers consider "tradition" a bad word. To put it very simply, for many of them, "Scripture good. Tradition, bad."
But, in fact, tradition is not always bad. Even human traditions are not always bad. So, let's go on with our analysis.
The Teaching of Jesus
So, what is this Doctrine, this Teaching, this Tradition which was passed down to us and we must pass down without altering? It is Christian Doctrine. The Teachings which Jesus commanded the Church to pass on in the Great Commission:
Matthew 28:18 Then Jesus came to them and said, “All authority in heaven and on earth has been given to me. 19 Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20 and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.”
Sound means Trustworthy
What does "sound" mean? Sound can mean many things depending on the context. It can mean "noise." Or "vocalization". Or other things, depending on the context. Let's look at the context in which it is used in the Bible when paired with doctrine.
2 Tim 4:3 For the time will come when people will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear.
So, sound doctrine is not necessarily what one wants to hear.
Titus 1:9 He must hold firmly to the trustworthy message as it has been taught, so that he can encourage others by sound doctrine and refute those who oppose it.
Sound doctrine is a "trustworthy message which has been passed down according to how it has been taught."
So, no deviations. No inventions. It must be passed down faithfully, according to how it was taught, originally.
And, must it be passed down by Scripture alone?
1 Thessalonians 2:13 And we also thank God continually because, when you received the word of God, which you heard from us, you accepted it not as a human word, but as it actually is, the word of God, which is indeed at work in you who believe.
You heard from us. Therefore, these were taught by word and not by reading it for themselves.
And it says "from us". Therefore, there is a select group from which one must learn the Teachings. As Scripture says elsewhere:
Hebrews 13:7 Remember them which have the rule over you, who have spoken unto you the word of God: whose faith follow, considering the end of their conversation.
Therefore, in order to receive a faithful and trustworthy message, one must learn it from the Sacred Traditions which are passed down by their leaders in the Church.
Conclusion
The Sacred Traditions of the Catholic Church are the sound doctrine which we need in order to understand the Word of God. They are the basis of the New Testament without which we have no anchor to keep us from floating away in a sea of inventions that are continually being brought about by those who prefer their own ideas that those of Jesus Christ.
If you want to be sure that you are receiving sound doctrine and that you are passing on dound doctrine, stick to the Traditions of the Catholic Church.