[the_conscience]

I agree the syllogism as written is not valid. Even if we add the 4th premise it still begs the question.

But the "fitting" argument as presented is likewise invalid.

We declare, pronounce and define that the doctrine which holds that the Blessed Virgin Mary, at the first instant of her conception, by a singular privilege and grace of the Omnipotent God, in virtue of the merits of Jesus Christ, the Saviour of mankind, was preserved immaculate from all stain of original sin, has been revealed by God, and therefore should firmly and constantly be believed by all the faithful.

Let's see how the argument is presented:

1. Mary is born.
2. Because of Jesus, Mary is immaculate.
Conc: God graced Mary at her birth to be immaculate.

The whole argument is out of order! It doesn't follow. There's nothing fitting about it.

[D-fendr]

Let's see how the argument is presented..

It's not an argument, it's a declaration of doctrine. It's not presented to be accepted on its logic or required to conform to reason, only faith, to "be believed by all the faithful."

[D-fendr]

Again: I don’t see this route as something you’d pursue in your path to a simple syllogism to prove that “Mary is not the mother of God.”

[Mad Dawg]

I am now officially confused. What you quoted wasn't an argument and didn't claim to be an argument. It was a "definition," in this case a statement of what is "de Fide".

What that means is that this is a statement of the essentials of the dogma. If somebody wants to talk about the dogma, he's got to take all the pieces into account or he's not talking about the dogma. It's a singular privilege and grace; it's done by the Omnipotent God; it's done in virtue of the merits of Jesus Christ (so, in other words, Mary didn't do it herself and it depends on what Jesus did), and she was sinless from the very beginning of her existence.

It's in no way an argument. It's, so to speak, the rules of what the dogma is. You'd have to read elsewhere in the encyclical to find where the arguing part happens.

And I thought I said that it was only in light of the dogma that I would say it was "fitting." God does everything well. If you think God 'did' the Incarnation and you think He 'did' the Immaculate Conception, then you can enjoy the thought that the perfect man was conceived and gestated and all the rest by a sinless mother.

But no serious theologian argues that because anything else would have been "unfitting" therefore He MUST have done the IC.

Again, I hope that's clear. It is as if you were looking at a law that was passed and expecting it to contain the explanation for why it was passed, or reading the verdict and expecting it to contain the evidence. I hope those analogies are useful.