500 years ago today—on July 10, 1509—one of the most important theologians in Christian history was born. John Calvin.

A second-generation reformer during the Protestant Reformation, Calvin was a scholar out of the Renaissance humanist tradition and produced a striking amount of scholarly output, including commentaries on most books of the Bible and his magnum opus, Institutes of the Christian Religion–one of the most significant systematic theologies ever written.

But he’s also known for Calvinism—the theological approach (also known as Reformed) that emphasizes things like God’s sovereignty, predestination, and the inherent depravity of man. And Calvinism, strange as it may seem to some, is now more popular than ever.