Simplify the following text for a Grade 12 native English-speaking person.
Original: Sola scriptura was a foundational doctrinal principle of the Protestant Reformation held by the Reformers and is a formal principle of Protestantism today ( see Five solas ) .
Simplified: Sola scriptura was a principle of the Protestant Reformation of the reformer Martin Luther and is a principle of Protestants today ( see Five solas ) .