I got these quotes from the following link-- I just copied the 1st sentence under "Proof from scripture" and some of the "Proof from Tradition." Didn't copy the whole thing just the parts I found interesting. This is a Catholic website.
CATHOLIC ENCYCLOPEDIA: Immaculate Conception
Proof from Scripture
Genesis 3:15
No direct or categorical and stringent proof of the dogma can be brought forward from Scripture
Proof from Tradition
In regard to the sinlessness of Mary the older Fathers are very cautious: some of them even seem to have been in error on this matter.
Origen, although he ascribed to Mary high spiritual prerogatives, thought that, at the time of Christ's passion, the sword of disbelief pierced Mary's soul; that she was struck by the poniard of doubt; and that for her sins also Christ died (Origen, "In Luc. hom. xvii").
In the same manner St. Basil writes in the fourth century: he sees in the sword, of which Simeon speaks, the doubt which pierced Mary's soul (Epistle 260).
St. Chrysostom accuses her of ambition, and of putting herself forward unduly when she sought to speak to Jesus at Capharnaum (Matthew 12:46; Chrysostom, Homily 44 on Matthew).
But these stray private opinions merely serve to show that theology is a progressive science. If we were to attempt to set forth the full doctrine of the Fathers on the sanctity of the Blessed Virgin, which includes particularly the implicit belief in the immaculateness of her conception, we should be forced to transcribe a multitude of passages. In the testimony of the Fathers two points are insisted upon: her absolute purity and her position as the second Eve (cf. 1 Corinthians 15:22).
I did not copy the Pope Pius IX Dec 8. 1854 article--those interested can search it--but
am I understanding correctly that this teaching did not become dogma until 1854??