After many years of theological debate, I've learned a crucial fact that I never even suspected at first: many people who claim to reject the definitive teaching of the Catholic Church on this or that point are really only rejecting theological opinions that, while having commonly accompanied the teachings, are not logically equivalent to them. Consistently with Catholic orthodoxy, it is quite possible to affirm the dogmas without buying into some of the accompanying theology. Yet many people don't realize that because they are unaware of the distinction, or at least of how it applies in particular cases. Much useless expenditure of breath could be avoided if the distinction between dogma and theology would be kept firmly and accurately in mind.
Three instances seem to crop up repeatedly: extra ecclesiam nulla salus ('EENS' for short), original sin, and the filioque. Since this is a blog not a book, I will state as briefly as I can how the distinction applies in each case.
The Catholic Church definitively teaches EENS: "outside the Church there is no salvation." That is solemnly defined dogma. But particular answers to the question what counts as being inside the Church are logically distinct from EENS. The dogmatic answer is that one is inside the Church just in case one is validly baptized; from that and EENS, it follows that "baptism" is necessary for salvation. But the question what counts as baptism in God's eyes is controversial at the margins.
There's sacramental baptism by water, which by definitive Church teaching is the "ordinary" means of admission to membership in the Church. That is uncontroversial. Nor is it particularly controversial that one can undergo the graced equivalent of baptism by means of martyrdom ("baptism of blood") or by dying as a sincere catechumen before one has the opportunity to be formally baptized ("baptism of explicit desire"). That such means suffice in the relevant cases has been infallibly taught by the "ordinary" magisterium of the Church. The controversy is over whether there is such a thing as baptism by desire that remains, for all we know, merely implicit. If there is, then it is quite possible that some people belong to the Church without ever knowing it in this life. Since the 19th century, and especially since Vatican II, that has become the common opinion among Catholics, including the previous and present popes. At the same time, a minority of traditional Catholics still adhere to the older view. The matter is one of theological opinion. But many people are under the impression that the Church has reversed EENS in virtue of the historic shift of opinion. She has not. What's changed is not the dogma that outside the Church there is no salvation, or even the dogma that baptism is necessary for salvation, but rather opinions about whether, in his mercy, God might well count as baptism something that is neither formal baptism nor an explicit desire for it. It's vital to remember that, so far, that issue remains one of opinion; yet most people, including most Catholics, seem totally unaware of that.
What about "original sin"? St. Augustine's view, which remained a common view in the Church for well over a millennium, was that original sin is inherited, personal guilt. That is the main reason why he taught that infants who die unbaptized go to hell to suffer punishment—albeit, of course, the "mildest" of punishments. But that view did not sit well with certain later theologians, such as Thomas Aquinas, who introduced the idea of the limbus infantium, "limbo," a state in which where infants who die unbaptized would enjoy eternal but purely "natural" happiness without the vision of God. That was the common opinion among Catholics from the High Middle Ages until, roughly, the time of Vatican II.
Aquinas tried to reconcile his view with Augustine's by positing that such infants unwittingly suffer a poena damni, a mild but poignant "pain of loss" in virtue of their being unable to enjoy "the beatific vision." But it's hard to see how that situation would be compatible with complete if natural happiness, and its presentation as a solution depends anyhow on the assumption that purely "natural" happiness is possible in the economy of grace. Most Catholic theologians now reject that view, which is why the hypothesis of limbo has fallen out of favor even at the highest levels of the Vatican. Even more tellingly, the Catechism of the Catholic Church explicitly denies that original sin is "personal fault"! So, the problem about the fate of unbaptized infants that Augustine and Aquinas took to be raised by the inheritance of original sin shows itself to be, in the end, artificial. If the theological opinion that original sin is personal guilt is in fact false, which is what the Catholic Church now definitively teaches, then there's no need for limbo and the question whether those who die without baptism or explicit desire for it can attain union with God remains open. But to hear the howls from the trads, you'd never know it. They confuse the old opinions with the dogma of original sin defined over a millennium after Augustine at the Council of Trent. While Augustine was obviously the single most important doctor of the Church in the development of that doctrine, the Church has not defined as dogma all his views thereon and indeed has come to reject his theory of massa damnata—the theory that all who die in original sin not only go to hell but deservedly stay there forever.
The filioque is the Catholic dogma that the Holy Spirit proceeds from the Father "and the Son." Assent to that dogma is a necessary condition for full communion with the Catholic Church. For reasons I don't have time to discuss here, and unlike many of my fellow Catholics, I consider that dogma quite important for such understanding of the dogma of the Trinity as God has given us to have. It developed in the West during the first millennium largely under the influence of St. Augustine's De Trinitate; by the time Rome inserted it into the Nicene-Constantinopolitan Creed in the 11th century, it had become the common faith of the Western Church. The Eastern Church never accepted it, and since the ninth century it has been the subject of much sterile logomachy between East and West. Given as much, I agree with the late historian of doctrine Jaroslav Pelikan that there's a special place in hell reserved for people who keep such logomachy alive, and I don't want to contribute to it here. What I want to do is show that the sense in which the filioque is dogmatically binding does not depend on distinctively Augustinian triadology.
It matters not what that triadology actually is; indeed, the interpretation of the De Trinitate has itself been one of the standard topics of the sterile logomachy. What matters is the dogma: the Holy Spirit proceeds from the Father and the Son, in the words of the 13th-century Council of Lyons, "as from one principle." That qualification was introduced by Rome as a concession to Byzantine concerns that the filioque not be taken to posit a "dual procession" of the Spirit from the Father and the Son, as though the Son "caused" the being of the Spirit in the same sense as the Father, who is the sole ultimate source of the being of others. All that's needed to derive the filioque, in fact,are two premises.
The first, which I take to be uncontroversial, is that the one God is essentially trihypostatic: it is of the essence of God that God be three persons who are each the same God as the others. From that it follows that, necessarily, each Person exists just in case the others do. Now if one grants a second premise, invoked by most Fathers and Doctors of the Church and consonant with the first, that the Spirit is necessarily the Spirit of the Father and the Son, then it follows further that the Spirit's "procession" ad intra entails that the Father originates the Spirit only as Father of the Son. That allows one to say that the Holy Spirit proceeds from the Father "and" the Son without thereby implying that the Son is a "cause" of the Spirit in the same way as the Father. The Father is indeed the sole ultimate source of being in the Godhead; but since he breathes forth the Spirit only as Father of the Son, the Spirit's procession also depends on the Father's generation of the Son. Thus the Spirit, as Spirit of the Father and the Son, proceeds from the Father and the Son.
On the premises I've used, of course, it also follows that the Father generates the Son only as the one who breathes forth the Holy Spirit. But it does not thereby follow that the Son is the Son of the Father and the Spirit. For the modes of origin of the Son and the Spirit are different: the Son's mode of origin is "generation" and the Spirit's is "procession." The only thing we can say about the difference between such generation and procession, while remaining safely grounded in the historic faith of the Church, is that the Spirit's procession depends on the Son's generation in some way that the latter does not depend on the former. That is why it should not be said that the Son is begotten by the Father and the Holy Spirit. But it would, I believe, be orthodox to say that the Son is begotten "in" the Holy Spirit. For the existence of each Person entails that of the others, and the Spirit is the Spirit of the Father and the Son.
The connective "and" in the filioque is unfortunately misleading because, even though it admits an orthodox interpretation, it is also susceptible to and even invites more than one heterodox interpretation. But the Orthodox theologian Theodore Stylianopoulos has suggested that there are ways around that; and the Catholic paradigm of "development of dogma" could surely accommodate some of those ways. Catholic theologians such as Thomas Weinandy, Paul Quay, and David Coffey have done good work in showing how. But the main point is that the thing can be done independently of theological speculations that were originally peculiar to Augustine and in that way gave impetus to the filioque's development. A lot more remains open than many Eastern critics of the filioque, and even some Western defenders thereof, seem to think.
My aim in discussing the three instances of EENS, original sin, and the filioque is to show how it is that the Catholic Church's development of doctrine, while conceptually dependent on historic theological context, is by no means the same thing and in fact yields results more modest than such theology usually does. Accordingly, some of the theology can be jettisoned without compromising dogma. If more people would appreciate that, there would be far less misunderstanding and logomachy than we usually see.