A few weeks ago I wrote on the Protestant notion of Sola Scriptura (by scripture alone). Recently, Mark Shea wrote a piece for Catholic Exchange on the same subject.
One basic rule of thumb to understand in Catholic / Protestant conversations is that it is not the case that Catholics rely on Sacred Tradition and Protestants don’t. Rather, Catholics (and, by this, I mean “educated Catholics speaking out of the Magisterial teaching of the Church”) rely on Sacred Tradition and know they do, while Protestants rely on (parts) of Sacred Tradition and (usually) don’t know they do.
So, for instance, despite Paul’s prescriptions (directed only at clergy of his day) that a man must be the husband of but one wife, nowhere in the text of Scripture is it made clear that Christian marriage must be monogamous for all (a fact that did not escape Luther or John Milton). Nowhere does Scripture spell out or that the Holy Spirit is a person, much less the Third Person of the Blessed Trinity, consubstantial with the Father and the Son. Similarly, you will look in vain for instructions in Scripture on how to contract a valid marriage (unless you buy this list of “Top 10 Ways to Find a Wife, According to the Bible”):
10. Find an attractive prisoner of war, bring her home, shave her head, trim her nails, and give her new clothes. Then she’s yours. – (Deuteronomy 21:11-13)
9. Find a prostitute and marry her. – (Hosea 1:1-3)
8. Find a man with seven daughters, and impress him by watering his flock. – Moses (Exodus 2:16-21)
7. Purchase a piece of property, and get a woman as part of the deal. – Boaz (Ruth 4:5-10)
6. Go to a party and hide. When the women come out to dance, grab one and carry her off to be your wife. – Benjaminites (Judges 21:19-25)
5. Have God create a wife for you while you sleep. – Adam (Genesis 2:19-24)
4. Kill any husband and take his wife. – David (2 Samuel 11)
3. Cut 200 foreskins off of your future father-in-law’s enemies and get his daughter for a wife – David (I Samuel 18:27)
2. Even if no one is out there, just wander around a bit and you’ll definitely find someone. – Cain (Genesis 4:16-17)
1. Don’t be so picky. Make up for quality with quantity. – Solomon (1 Kings 11:1-3)
…which doesn’t really help much. The fact is, the Bible says “Marriage is good” but gives us not one word of instruction on how to do it. That’s because Scripture is not and never was intended to be the Big Book of Everything. And yet, of course, Protestants all over the world get married, believe in God the Holy Spirit, and have but one spouse because, as James Dobson says, God’s plan is one man and one woman. How do they do this when Scripture is so unclear?
Read the whole article: The Semi-Permeable Membranes of the Various Protestantisms