Institutes of the Christian Religion
Although not shaped by Luther's doctrine, Calvinist churches throughout the world do not regard the Reformation Day as less important, and celebrate it in a similar manner to Lutherans. The nailing of the "Ninety-five Theses" sparked the discussion about Catholic beliefs and practices of the day. Reformed theology first emerged in 1516 with Huldrych Zwingli in Switzerland who decided to participate in this European-wide discussion after seeing Luther's postulates; all this would not have happened without the events of 31 October 1517. French lawyer John Calvin joined the theological conversation in 1536 with publication of his Institutes of the Christian Religion.