Nothing about the founders seems as interesting or as timely to us, 200 years and more farther on, as their religious views — who, if Anyone, they worshiped, how they marked the boundaries of church and state. As a Washington biographer, I have been assured, during the Q. and A. periods after talks, that George Washington saw the Virgin Mary at Valley Forge and converted to Roman Catholicism on his deathbed (why wait, if he had seen the Virgin 21 years earlier?). I was also once asked if he was an “illuminated Freemason”; I sped away from that question as fast as possible. Whether in legal briefs or op-ed articles, we are as passionate about religion as the founders were. Unfortunately, our passions make for a lot of sloppy and willful historical thinking and writing. In “Founding Faith,” Steven Waldman, a veteran journalist and co-founder of Beliefnet.com, a religious Web site, surveys the convictions and legacy of the founders clearly and fairly, with a light touch but a careful eye.