[aruanan]

Why do we believe in the Immaculate Conception?

1. Because someone said so? An appeal to authority?
2. Because a tendency toward docetism had to come up with a dodge to keep Jesus from being tainted by sinful flesh.

[Tantumergo]

"2. Because a tendency toward docetism had to come up with a dodge to keep Jesus from being tainted by sinful flesh."

I think St. John's corpus of writing more than adequately dealt with the Docetist heresy, and yet his devotion to the Ark of the New Covenant is very profound.

Better try harder than that.