Complex sentence: Historian and ethicist John G. Stackhouse, Jr. provided historical context for "The Secret," critically locating it in the tradition of American "New Thought" and "mind over matter" philosophy and popular religion in his weblog, calling it "nothing new".
Split into simpler sentences: Historian and ethicist John G. Stackhouse, Jr. in his weblog provided historical context for "The Secret". He critically located it in the tradition of American New Thought, a "mind over matter" philosophy, and popular religion, calling it "nothing new".