And how do we know that all of the NT writers wrote by the inspiration of God? Because, under the guidance of the Holy Spirit, the Catholic Church discerned which writings were inspired by that same Spirit.
Protestantism is odd when you really think about it. It takes from Catholic teaching only what it wants and then claims that the Church is wrong on those points. I would be more inclined to believe that if the Catholic Church is that wrong about so many things then how could they be right about the Bible?
And 2nd Timothy 3:16 SAID that all scripture was written under the inspiration of God. S’nuff for me.