Protestantism, from Martin Luther until today, has declared that the Bible is the sole authority of Christianity. Therefore the first Protestant Challenge is to find somewhere in the Bible where it says that the scriptures are the sole authority of Christianity.
I am not looking for scriptures that say that the Bible is authoritative, true, or profitable. All of these we can agree upon. The disagreement is whether it is the sole authority.
Despite what is clearly written in the book of James most of Protestantism believes that we are saved by faith alone. The second Protestant Challenge is to find within the canon of scriptures where it says we are saved by faith alone.
To understand this challenge you must understand that the Orthodox view of salvation includes everything from Baptism to when we have our glorified body in Heaven.
I am not looking for scriptures that say we are saved by faith; they are obvious and abundant. To win the Protestant Challenge you must find scriptures, which specifically say, we are saved by faith alone.
Paul said that we as Christians should be of one mind and have no divisions amongst us. When confronted with Paul’s claim, many of the Protestants I speak to say they are united over the primary or important doctrines, which deal with our salvation. They, however, disagree on the secondary or unimportant ones that don’t affect our salvation.
The third Protestant Challenge is to find in the Scriptures this idea of primary and secondary doctrines.
The fourth Protestant challenge is to show when and where this change happened. For example show that the Church believed one thing in the second century and changed it in the fourth.
I am not interested in personal disagreement with any particular Church doctrine, but in historical evidence of a change.