So absent a statement of Mary being a sinner, one concludes that he believed her sinless? Did Athanasius affirm this:
Hebrews 4:14-16
14 Seeing then that we have a great High Priest who has passed through the heavens, Jesus the Son of God, let us hold fast our confession. 15 For we do not have a High Priest who cannot sympathize with our weaknesses, but was in all points tempted as we are, yet without sin. 16 Let us therefore come boldly to the throne of grace, that we may obtain mercy and find grace to help in time of need.
Or this:
Romans 3:22-24
22 even the righteousness of God, through faith in Jesus Christ, to all and on all[a] who believe. For there is no difference; 23 for all have sinned and fall short of the glory of God, 24 being justified freely by His grace through the redemption that is in Christ Jesus,
Considering the type of man he was, one wonders how one so scholarly could affirm the above and then not wonder where the verse concerning Mary's sinlessness can be found. And if believed sinless, why not as an article of the catholic faith of which he wrote so forcefully. Perhaps Athanasius recognized the Incarnation for what is was: God's mighty act, not God's with Mary's help.
Mary simply followed the will of God and could have rejected it just like you and I do when we sin.
God eternally knew Mary would follow perfection,thus the Incarnation was perfection of Mary following the will of God
Why do you cheapen the Incarnation as if Christ had to be Incarnated with a sinful Mother?