1 At this very troublesome and difficult time, the hidden designs of God have conducted Our poor strength to the office of Supreme pastor, to rule the entire flock of Christ. The enemy has, indeed, long been prowling about the fold and attacking it with such subtle cunning that now, more than ever before, the prediction of the Apostle to the elders of the Church of Ephesus seems to be verified: "I know that . . . fierce wolves will get in among you, and will not spare the flock." Those who still are zealous for the glory of God are seeking the causes and reasons for this decline in religion. Coming to a different explanation, each points out, according to his own view, a different plan for the protection and restoration of the kingdom of God on earth. But it seems to Vs, Venerable Brethren, that while we should not overlook other considerations, We are forced to agree with those who hold that the chief cause of the present indifference and, as it were, infirmity of soul, and the serious evils that result from it, is to be found above all in ignorance of things divine. This is fully in accord with what God Himself declared through the Prophet Osee: "And there is no knowledge of God in the land. Cursing and lying and killing and theft and adultery have overflowed: and blood hath touched blood. Thereafter shall the land mourn, and everyone that dwelleth in it shall languish."
Source: Acerbo Nimis (Vatican.va)