Many people outside the Catholic Church cannot understand why she is so seemingly intransigent in the face of strong appeals to join in world-wide movements for unity among other Christian communities. This book, by describing the age-long gtrugg-le to preserve the true faith, shows the reasons for this refusal to compromise. It is at the same time a guide througt the maze of “-isms” that name the innumerable heresies and a survey of the entire range of heretical beliefs from the Judaizing Christians and Gnostics who figure in the Acts of the Apostles, through such tenacious errors as Manicheism with its medieval successors among the Albigensians and the Cathari, the Donatists and Pelagians opposed by St Augustine, the Arians and Nestorians, the movement's Led by Wyclif and Huss down to the major schism of the Reformation and the great heresies of the seventeenth century, Jansenism and Quietism. Subsequent chapters are devoted to the various kinds of Naturalism, Modernism, Anglicanism and the sects stemming from it, together with a consideration of the Catholic Church in relation to the Ecumenical movement and such bodies as the World Council of Churches.