VATICAN CITYFor decades, many liberation theologians globally have lived with a looming possibility: One day, a letter could arrive from the Vatican contesting their work, even calling it heretical or anti-Christian.Mounting a defense could take years, with long, confidential letters sent back and forth to the Vatican's powerful Congregation for the Doctrine of the Faith. For lay people, non-compliance could mean losing university tenure. For priests, brothers, and sisters, it could mean an order of silence or even removal from your religious order.But in a unique turn of events, the theologian credited with founding the sometimes-controversial liberation theology movement was invited to speak at the Vatican Tuesday by none other than the current leader of its doctrinal office, Cardinal Gerhard Müller.Dominican Fr. Gustavo Gutierrez was a surprise guest and speaker during a book launch for a new book by the cardinal, titled Poor for the Poor: The Mission of the Church. The book, which has a preface from Pope Francis, also has two chapters written by the theologian and is largely focused on explaining — sometimes even defending — liberation theology.In interviews with press Tuesday before the event, Müller wholeheartedly backed liberation theology, saying it "is based on a theology of the word and is not a human ideology."