Margaret Downey, president of the Freethought Society of Greater Philadelphia, will talk about why her FFRF chapter erects a "Tree of Knowledge" every year by a courthouse creche and how officials have tried to sabotage that solstice observance. Well-known journalist Hanna Rosin will talk about her cover story in the December Atlantic: "Did Christianity Cause the Crash? How Preachers Are Spreading a Gospel of Debt." The hosts will replay Ken Lonnquist's "O Isthmus Tree."