If the unity, promised by God-incarnate, is to be secured, the present circumstances of the case, as well as the actual experience of many centuries, prove three conditions to be absolutely necessary, viz.: a teacher who is firstly ever living and accessible; secondly, who can and will speak clearly and without ambiguity; and thirdly, and most essential of all, whose decisions are authoritative and decisive. One, in a word, who can pass sentence and close a controversy, and whose verdict will be honoured and accepted as final by all Catholics without hesitation. These three requisites are found in the person of the infallible Head of the Catholic Church, but nowhere else.
Experience shows that where, in religion, there is nothing but mere human learning to guide, however great such learning may be, there will always be room left for some differences of opinion. In such controversies even the learned and the well read will not all arrange themselves on one side; but will espouse, some one view, and some another. We find this to be the case everywhere. And, since the Church of England offers us as striking and as ready an example as any other, we cannot do better than invoke it as both a warning and a witness.
Though her adherents are but a small fraction, compared with ourselves, and though they are socially and politically far more homogeneous than we Catholics, who are gathered from all the nations of the earth, yet even they, in the absence of any universally recognised and infallible head, are split up into a hundred fragments.