The question I posed: According to the Catholic Church, why did God create Mary to be without sin from the first moment of her conception?
Answer: Because it was "wholly fitting" that the Mother of God be perfectly pure, without taint of sin.
I said it was sort of a trick question because I really wanted to focus attention on what Mother Church does NOT say. She does NOT say that it was "necessary" in any way that Mary be sinless so that she would not pass along Original Sin to Jesus. Because if that were the case (as Lauren pointed out), then St. Anne would have had to be sinless to bear a sinless Mary, and on and on all the way back through the generations.
It's amazing how many really sound and faithful Catholics believe (wrongly) that Mary's Immaculate Conception was necessary. I know a wonderfully orthodox Catholic who wrote a brilliant catechism which had this error in it. I pointed it out to him, and he just could not see the illogic of using that argument. I have even heard wonderful priests preach this error from the pulpit.
Anyway, it's just a little pet peeve of mine, so I wanted to clear that up.
So, in a nutshell, the "why" of it is because it was fitting, not because it was necessary.
(Find the entire encyclical defining the dogma of the Immaculate Conception here.)
The awesome answers you all offered really fleshed it out even more, diving into the understanding of Mary as Ark of the New Covenant, Mary as the New Eve. She is all that! And the encyclical above discusses those themes as well. Man, you guys are good. It also gets me excited about writing more on Mary as New Ark and New Eve. That is some amazing stuff!! Blows me away, really, so I will revisit that for sure.
Finally, what you have really been waiting for...
The Bubble Awards!
I am limiting these to six awards, or else I will end up giving one to everyone. The envelopes, please....
The Speedy Gonzales Award goes to Sew Infertile, for her quick response like last time! Secondary award for being the second commenter, commenting on her first comment. By the way, Sew will always get an award, just because she is Sew. I think that is, well, wholly fitting. ;)
The Patriot Award for Best Use of a Decoy Link in Order to Instruct Americans About Flag Etiquette goes to Cathy!
The Most Courageous Emergence of a Protestant Into the "Little Catholic Bubble" Award goes to Olya! I speak for everyone when I say that you are always welcome here!
The Most Likely to Have Written Her Comments From a Bar Award goes to Jenny!
The Flattery Will NOT Get You an Award Award goes to Shannon, for making me feel good about changing my blog design in the shameful and obvious hope of getting an award. Clearly that didn't work, but nice try!
And finally, the That's Pretty Much Exactly the Answer I Was Looking For Award goes to Lauren! I will ignore the fact that she confessed a grave sin from the last Doctrinal Quiz Show (although she will have to give back her Frank Sheed award), and I will also try to ignore her explicitly voiced complaint about my question. The fact that I still give her this coveted award is a testament to my good will, fair-mindedness, spirit of forgiveness, extreme generosity and almost unimaginable humility.
Now, please, don't despair if you didn't win a Bubble Award this time, because the rest of you won the Scarlett O'Hara Award for remembering that tomorrow is another day.
PS: Second Chances, you are still brown-nosing. ;)