The Syllabus of Pius IX. has been the subject of so many misconceptions, that a plain and simple setting forth of its meaning cannot be useless. This is what I have tried to do in the following pages. A vindication or defence of the Syllabus was, of course, out of the question in so small a compass; but I think more than half the work of defence is done by a simple explanation. During the ten years just completed since its promulgation, much has occurred to shew the wisdom that dictated it. The translation I have given is the one authorized by His Eminence the Cardinal Archbishop of Dublin.