Philipp Melanchthon was a German Reformer. He accepted a call to the University of Wittenberg from Martin Luther on the recommendation of his great-uncle, and became professor of Greek there at the age of 21. He developed a father-son relationship with Luther, even though they were completely opposite in personality. Melanchthon is the first systematic theologian of the Reformation, and an influential designer of educational systems. He stands next to Luther and John Calvin as a reformer, theologian, and molder of Protestantism.