The teaching of the nineteenthcentury popes was not erroneous, but was limited by the political and social horizons of the time. In the words of DH, Vatican II brought forth from the Churchs treasury "new things in harmony with those that are old." This process of development must continue as the Church faces the new problems and opportunities that arise in successive generations.
I'm afraid I must take issue with Avery Cardinal Dulles. I believe that his treatment would perfectly solve the issues at stake, but here is the rub. When Pius IX, Leo XIII, and St. Pius X (among other many other Popes) discuss the duties of the State towards the true religion, they present these duties as coming from nature itself. Whereas this is what Cardinal Dulles said of DH:
"Regarding the second point, the Council taught that the State has an obligation to protect the inviolable rights of all citizens, including the right of religious freedom.
It did not teach that the State was obliged to give legal privileges to Christianity or Catholicism, although it did not rule out such arrangements. It did deny that civil government had the authority to command or prohibit religious acts."
The aforementioned Popes taught precisely the opposite, that it was not only a matter of political expedience for Christianity (Catholicism) to be the religion of the state, but an obligation on the state based in the very Rights of Christ the King over all of human society. Leo XIII deals with this exact issues in
Libertas and St. Pius X likewise expounds the necessity of the confessionally Catholic State in
Vehementer Nos. They do not present their demands as temporally limited, but rather universally applicable.
Libertas: 21. "This kind of liberty, if considered in relation to the State, clearly implies that there is no reason why the State should offer any homage to God, or should desire any public recognition of Him; that no one form of worship is to be preferred to another, but that all stand on an equal footing, no account being taken of the religion of the people, even if they profess the Catholic faith. But, to justify this, it must needs be taken as true that the State has no duties toward God, or that such duties, if they exist, can be abandoned with impunity, both of which assertions are manifestly false. For it cannot be doubted but that, by the will of God, men are united in civil society; whether its component parts be considered; or its form, which implies authority; or the object of its existence; or the abundance of the vast services which it renders to man. God it is who has made man for society, and has placed him in the company of others like himself, so that what was wanting to his nature, and beyond his attainment if left to his own resources, he might obtain by association with others. Wherefore, civil society must acknowledge God as its Founder and Parent, and must obey and reverence His power and authority. justice therefore forbids, and reason itself forbids, the State to be godless; or to adopt a line of action which would end in godlessness -- namely, to treat the various religions (as they call them) alike, and to bestow upon them promiscuously equal rights and privileges. Since, then, the profession of one religion is necessary in the State, that religion must be professed which alone is true, and which can be recognized without difficulty, especially in Catholic States, because the marks of truth are, as it were, engraven upon it. This religion, therefore, the rulers of the State must preserve and protect, if they would provide -- as they should do -- with prudence and usefulness for the good of the community. For public authority exists for the welfare of those whom it governs; and, although its proximate end is to lead men to the prosperity found in this life, yet, in so doing, it ought not to diminish, but rather to increase, man's capability of attaining to the supreme good in which his everlasting happiness consists: which never can be attained if religion be disregarded. "
Vehementer Nos: 3. That the State must be separated from the Church is a thesis absolutely false, a most pernicious error. Based, as it is, on the principle that the State must not recognize any religious cult, it is in the first place guilty of a great injustice to God; for the Creator of man is also the Founder of human societies, and preserves their existence as He preserves our own. We owe Him, therefore, not only a private cult, but a public and social worship to honor Him. Besides, this thesis is an obvious negation of the supernatural order. It limits the action of the State to the pursuit of public prosperity during this life only, which is but the proximate object of political societies; and it occupies itself in no fashion (on the plea that this is foreign to it) with their ultimate object which is man's eternal happiness after this short life shall have run its course. But as the present order of things is temporary and subordinated to the conquest of man's supreme and absolute welfare, it follows that the civil power must not only place no obstacle in the way of this conquest, but must aid us in effecting it. The same thesis also upsets the order providentially established by God in the world, which demands a harmonious agreement between the two societies. Both of them, the civil and the religious society, although each exercises in its own sphere its authority over them. It follows necessarily that there are many things belonging to them in common in which both societies must have relations with one another. Remove the agreement between Church and State, and the result will be that from these common matters will spring the seeds of disputes which will become acute on both sides; it will become more difficult to see where the truth lies, and great confusion is certain to arise. Finally, this thesis inflicts great injury on society itself, for it cannot either prosper or last long when due place is not left for religion, which is the supreme rule and the sovereign mistress in all questions touching the rights and the duties of men. Hence the Roman Pontiffs have never ceased, as circumstances required, to refute and condemn the doctrine of the separation of Church and State. Our illustrious predecessor, Leo XIII, especially, has frequently and magnificently expounded Catholic teaching on the relations which should subsist between the two societies. "Between them," he says, "there must necessarily be a suitable union, which may not improperly be compared with that existing between body and soul.-"Quaedam intercedat necesse est ordinata colligatio (inter illas) quae quidem conjunctioni non immerito comparatur, per quam anima et corpus in homine copulantur." He proceeds: "Human societies cannot, without becoming criminal, act as if God did not exist or refuse to concern themselves with religion, as though it were something foreign to them, or of no purpose to them.... As for the Church, which has God Himself for its author, to exclude her from the active life of the nation, from the laws, the education of the young, the family, is to commit a great and pernicious error. -- "Civitates non possunt, citra scellus, gerere se tamquam si Deus omnino non esset, aut curam religionis velut alienam nihilque profuturam abjicere.... Ecclesiam vero, quam Deus ipse constituit, ab actione vitae excludere, a legibus, ab institutione adolescentium, a societate domestica, magnus et perniciousus est error."[1]
Furthermore, there is the additional problem that DH does not merely present religious liberty as a matter of political prudence, but as a civil
right. Leo XIII (in
Libertas) specifically rejects the idea that such rights are inherent in the human person, stating that error can have no rights and thus there can be no right to hold, proclaim, and propagate false religions.
Regrettably, I believe that Cardinal Dulles attempt at reconciling DH and the past teaching fails, because it is based on the premise that the traditional teaching on the Rights of Christ is time-bound and subject to change. He presents the traditional teaching as a phenomenon of the 19th century, but St. Pius X affirmed the same things in the 20th century, and Pius VI taught them in the 18th century. In light of the fact that St. Thomas Aquinas defended the right of the state to execute heretics, I'd say it goes back to the 13th century and beyond. Why, in Pius VII's condemnation of religious liberty (from
Post tam diuturnitas), he even quotes St. Augustine:
"A new source of pain with which Our heart is afflicted still more sharply, and which, We acknowledge, causes us an extreme tomrment, dejection, and anguish, is the twenty second article of the constitution (ed: the French Constitution). Not only is freedom of forms of worship and of conscience permitted there, to use the very terms of this article, but there is promised support and protection to this liberty, and besides to the ministers of what are called the cults There is be sure no need of long discourses, addresseing ourselves to such bishops as you, to make you recognize cleralry with what a mortal wound the Catholic religion in france finds itself struck by this article.
By the fact itself that liberty of all the cults without distiniction is established, truth is intermingled with error, and the holy and immaculate Spouse of Christ, the Church outside of which there can be no salvation, is put into a class with the heretical sects and even with the Jewish perfidy. Moreover, by promising favor and support to th esects of the heretics and to their ministers on tolerates and favors not only their persons but also their errors. It is implicitly this disasterous and forever deplorable heresy that
St. Augustine mentions in these terms: "It affirms that all the heretics are on the right path and speak the truth, and absurdity so monstrous that I cannot believe that any sect professes it."
Can it anywhere be found in the teaching of the Magisterium, that any of the Popes asserted that these things were bound only to the time period, and fully subject to change? Cardinal Dulles simply puts this forth as being the case, without offering any textual evidence whatsoever. Were the Popes unaware that their teachings weren't timeless?
I've offered a number of different sources here, admittedly I have not ordered them as well as I might. It is my invitation to you and to anyone else that may read this thread, that they go back and read these encyclicals in their entirety and for themselves. I especially recommend
Libertas but there are many others which deal with these subjects. The above quotes by no means exhaust the Magisterial treatment of this issue.