The first major religious change advocated by such reformers as Calvin and Luther was making the Bible widely available in the vernacular. In the Roman Catholic Church, the Bible had been read primarily in the Latin of St. Jerome (known as the Vulgate), a language not known by many of the laity.
The vernacular Bible was a notion grounded in another belief of the reformers, the "sola scriptura" doctrine, or the belief that scripture alone was necessary for salvation. This was a major contrast to the Roman Catholic doctrine that "Salus extra ecclesiam non est". (that there is no salvation outside the Church).