The first and fundamental question to be determined is: What is the precise weight to be ascribed to the Syllabus, or, rather, what is its doctrinal authority? On the manner in which we reply to this depends the solution of numerous practical difficulties which interest consciences, and which have more than once been the subject of the polemic of the journals themselves. For example, are the decisions of the Syllabus unchangeable; is it not possible that they should be modified some day; is it certain they will never be withdrawn; are Catholics obliged to accept them as an absolute rule of their beliefs, or may they content themselves with doing nothing exteriorly in opposition to them? It is understood, in fact, that if we are in presence of an act wherein the successor of S. Peter exercises his sovereign and infallible authority, the doctrine is irrevocably, eternally, fixed without possible recall; and, by an inevitable corollary, the most complete submission, not of the heart only, but also of the intelligence, becomes an obligation binding on the conscience of the Catholic which admits of no reserve or subterfuge. If, on the contrary, the step taken by the Pope is merely an act of good administration or discipline, the door remains open for hopes of future changes, the constraint imposed on the minds of men in the interior forum is much less rigorous; a caviller would remain in Catholic unity provided that, with the respectful silence so dear to the Jansenists, he should also practise proper obedience. Now, the question, in the terms in which we have stated it, although treated of at various times by writers of merit, has not always been handled in a complete manner. Writers have been too often contented with generalities, with approaching only the question, and nothing has been precisely determined. Some have asserted, with much energy, the necessity of this submission, but they have not sufficiently defined its extent and nature. Others have dwelt upon the deference and profound respect with which every word of the Holy Father should be received, but, not having given any further explanation, they have left us without the necessary means for ascertaining what precisely they intended. Others have ventured to insinuate that the Syllabus was perhaps merely an admonition, a paternal advice benevolently given to some rash children, to which such as are docile are happy to conform, without feeling themselves under the absolute necessity of adopting it. Others, more adventurous still, have been unwilling to see more in it than a mere piece of information, an indication. According to these, Pius IX., wishing to notify to all the bishops of Christendom his principal authoritative acts since the commencement of his pontificate, had caused a list of them to be drawn out, and to be forwarded to them. The Syllabus was this illustrious catalogue, neither more nor less.