Calvinism became an important form of Protestantism by the mid-sixteenth century because of its emphasis on predestination and the idea of a "calling" or vocation. These ideas appealed to many people because they offered a sense of purpose and meaning in life, as well as a belief in salvation through faith alone. Additionally, Calvinism was seen as a more intellectually rigorous and organized form of Protestantism, with a strong emphasis on education and the study of the Bible. The spread of Calvinism was also aided by the influence of John Calvin, a prominent theologian and religious leader who established a strong following in Geneva, Switzerland. Overall, Calvinism's emphasis on predestination, vocation, education, and organization helped to make it a popular and influential form of Protestantism in the mid-sixteenth century.