Final answer:
Martin Luther was the church reformer who developed the idea of sola scriptura, fundamentally changing Christian theology and practice by emphasizing the Bible as the sole authoritative source for faith and life.
Step-by-step explanation:
The idea of sola scriptura, which asserts that the Bible is the sole infallible source of authority for Christian faith and practice, was developed by Martin Luther. Luther was a German monk and theologian who sparked the Protestant Reformation by posting his '95 Theses' on the door of the Castle Church in Wittenberg in 1517.
The concept of sola scriptura was central to Luther's teachings, as he contended that scripture alone should be the source of Christian belief and practice, contrasting with the Roman Catholic Church's emphasis on tradition and ecclesiastical authority alongside the Bible.
Luther's emphasis on the Bible and his rejection of the sale of indulgences and other church practices led to a fundamental shift in Christian theology and practice. His translation of the Bible into German made it accessible to a wider audience, and the invention of the printing press enabled his ideas to spread rapidly. As a result, various traditional Catholic practices were abandoned in favor of a direct engagement with the scriptures.