<P> At the age of twenty - six , Calvin published the first edition of his Institutes of the Christian Religion ( Latin title : Institutio Christianae Religionis ) , a seminal work in Christian theology that is still read by theological students today . It was published in Latin in 1536 and in his native French in 1541 , with the definitive editions appearing in 1559 ( Latin ) and in 1560 ( French ) . The book was written as an introductory textbook on the Protestant faith for those with some learning already and covered a broad range of theological topics from the doctrines of church and sacraments to justification by faith alone and Christian liberty , and it vigorously attacked the teachings of those Calvin considered unorthodox , particularly Roman Catholicism to which Calvin says he had been `` strongly devoted '' before his conversion to Protestantism . The overarching theme of the book -- and Calvin 's greatest theological legacy -- is the idea of God 's total sovereignty , particularly in salvation and election . </P>
what work written by calvin became the textbook for reformed theology
Institutes of the Christian Religion