The first edition of this little book was published in 1945. As indicated in this its opening paragraph, it was written in reply to the publication of an abridged edition of the celebrate work of George Salmon, The Infallibility of the Church. it has been decided to republish my reply to Salmon with only minor corrections, largely of misprints. But since its first appearance the second Vatican Council has taken place, and the ecumenical climate in this country has changed for the better. It may be helpful to refer here to Vaticans II's treatment of the themes of scripture and tradition, episcopal collegiality, and the status of non-Catholic Christians and their churches or ecclesial communities.