Like most 24-year-old men, Stephen Jones is keenly interested in sin. But while many of his peers enjoy their youthful indiscretions, Jones takes a more, shall we say, Puritanical stand. The weekend of June 12-15, Jones and 4,000 other young Christians packed into a convention center in Palm Springs, Calif., to hear preachers tell them that they are totally depraved, incapable of doing the right thing without a mighty hand from God, and -- most importantly -- have absolutely no control over their eternal fate. The mind behind that message is John Calvin, the 16th-century Reformer often better known for condemning sinners and heretics than for igniting evangelical zeal. But as Presbyterian and other Reformed churches prepare for the 500th birthday of their spiritual godfather on July 10, increasingly, it is young American evangelicals who are taking up his theological torch.