From New Advent Catholic Encyclopedia http://www.newadvent.org/cathen/11312a.htm#VI
As I'm not sure as to the reliability of this overview, I wonder if those more knowledgeable in Catholic Doctrine might like to comment. ORIGINAL SIN
Original sin may be taken to mean: (1) the sin that Adam committed; (2) a consequence of this first sin, the hereditary stain with which we are born on account of our origin or descent from Adam.
From the earliest times the latter sense of the word was more common, as may be seen by St. Augustine's statement: "the deliberate sin of the first man is the cause of original sin" (De nupt. et concup., II, xxvi, 43). It is the hereditary stain that is dealt with here. As to the sin of Adam we have not to examine the circumstances in which it was committed nor make the exegesis of the third chapter of Genesis.
II. PRINCIPAL ADVERSARIES
Theodorus of Mopsuestia opened this controversy by denying that the sin of Adam was the origin of death. (See the "Excerpta Theodori", by Marius Mercator; cf. Smith, "A Dictionary of Christian Biography", IV, 942.) Celestius, a friend of Pelagius, was the first in the West to hold these propositions, borrowed from Theodorus: "Adam was to die in every hypothesis, whether he sinned or did not sin. His sin injured himself only and not the human race" (Mercator, "Liber Subnotationem", preface). This, the first position held by the Pelagians, was also the first point condemned at Carthage (Denzinger, "Enchiridion", no 101-old no. 65). Against this fundamental error Catholics cited especially Rom., v, 12, where Adam is shown as transmitting death with sin. After some time the Pelagians admitted the transmission of death -- this being more easily understood as we see that parents transmit to their children hereditary diseases- but they still violently attacked the transmission of sin (St. Augustine, "Contra duas epist. Pelag.", IV, iv, 6). And when St. Paul speaks of the transmission of sin they understood by this the transmission of death. This was their second position, condemned by the Council of Orange [Denz., n. 175 (145)], and again later on with the first by the Council of Trent [Sess. V, can. ii; Denz., n. 789 (671)]. To take the word sin to mean death was an evident falsification of the text, so the Pelagians soon abandoned the interpretation and admitted that Adam caused sin in us. They did not, however, understand by sin the hereditary stain contracted at our birth, but the sin that adults commit in imitation of Adam. This was their third position, to which is opposed the definition of Trent that sin is transmitted to all by generation (propagatione), not by imitation [Denz., n. 790 (672)]. Moreover, in the following canon are cited the words of the Council of Carthage, in which there is question of a sin contracted by generation and effaced by generation [Denz., n. 102 (66)]. The leaders of the Reformation admitted the dogma of original sin, but at present there are many Protestants imbued with Socinian doctrines whose theory is a revival of Pelagianism.
III. ORIGINAL SIN IN SCRIPTURE
The classical text is Rom., v, 12 sqq. In the preceding part the apostle treats of justification by Jesus Christ, and to put in evidence the fact of His being the one Saviour, he contrasts with this Divine Head of mankind the human head who caused its ruin. The question of original sin, therefore, comes in only incidentally. St. Paul supposes the idea that the faithful have of it from his oral instructions, and he speaks of it to make them understand the work of Redemption. This explains the brevity of the development and the obscurity of some verses. We shall now show what, in the text, is opposed to the three Pelagian positions:
The sin of Adam has injured the human race at least in the sense that it has introduced death -- "Wherefore as by one man sin entered into this world and by sin death; and so death passed upon all men". Here there is question of physical death. first, the literal meaning of the word ought to be presumed unless there be some reason to the contrary. Second, there is an allusion in this verse to a passage in the Book of Wisdom in which, as may be seen from the context, there is question of physical death. Wis., ii, 24: "But by the envy of the devil death came into the world". Cf. Gen., ii, 17; iii, 3, 19; and another parallel passage in St. Paul himself, I Cor., xv, 21: "For by a man came death and by a man the resurrection of the dead". Here there can be question only of physical death, since it is opposed to corporal resurrection, which is the subject of the whole chapter.
Adam by his fault transmitted to us not only death but also sin, "for as by the disobedience of one man many [i.e., all men] were made sinners" (Romans 5:19). How then could the Pelagians, and at a later period Zwingli, say that St. Paul speaks only of the transmission of physical death? If according to them we must read death where the Apostle wrote sin, we should also read that the disobedience of Adam has made us mortal where the Apostle writes that it has made us sinners. But the word sinner has never meant mortal, nor has sin ever meant death. Also in verse 12, which corresponds to verse 19, we see that by one man two things have been brought on all men, sin and death, the one being the consequence of the other and therefore not identical with it.
Since Adam transmits death to his children by way of generation when he begets them mortal, it is by generation also that he transmits to them sin, for the Apostle presents these two effects as produced at the same time and by the same causality. The explanation of the Pelagians differs from that of St. Paul. According to them the child who receives mortality at his birth receives sin from Adam only at a later period when he knows the sin of the first man and is inclined to imitate it. The causality of Adam as regards mortality would, therefore, be completely different from his causality as regards sin. Moreover, this supposed influence of the bad example of Adam is almost chimerical; even the faithful when they sin do not sin on account of Adam's bad example, a fortiori infidels who are completely ignorant of the history of the first man. And yet all men are, by the influence of Adam, sinners and condemned (Romans 5:18, 19). The influence of Adam cannot, therefore, be the influence of his bad example which we imitate (Augustine, "Contra julian.", VI, xxiv, 75).
On this account, several recent Protestants have thus modified the Pelagian explanation: "Even without being aware of it all men imitate Adam inasmuch as they merit death as the punishment of their own sins just as Adam merited it as the punishment for his sin." This is going farther and farther from the text of St. Paul. Adam would be no more than the term of a comparison, he would no longer have any influence or causality as regards original sin or death. Moreover, the Apostle did not affirm that all men, in imitation of Adam, are mortal on account of their actual sins; since children who die before coming to the use of reason have never committed such sins; but he expressly affirms the contrary in the fourteenth verse: "But death reigned", not only over those who imitated Adam, but "even over them also who have not sinned after the similitude of the transgression of Adam." Adam's sin, therefore, is the sole cause of death for the entire human race. Moreover, we can discern no natural connexion between any sin and death. In order that a determined sin entail death there is need of a positive law, but before the Law of Moses there was no positive law of God appointing death as a punishment except the law given to Adam (Genesis 2:17). It is, therefore, his disobedience only that could have merited and brought it into the world (Romans 5:13, 14). These Protestant writers lay much stress on the last words of the twelfth verse. We know that several of the Latin Fathers understood the words "in whom all have sinned", to mean, all have sinned in Adam. This interpretation would be an extra proof of the thesis of original sin, but it is not necessary. Modern exegesis, as well as the Greek Fathers, prefer to translate "and so death passed upon all men because all have sinned". We accept this second translation which shows us death as an effect of sin. But of what sin? "The personal sins of each one", answer our adversaries, "this is the natural sense of the words `all have sinned.'" It would be the natural sense if the context was not absolutely opposed to it. The words "all have sinned" of the twelfth verse, which are obscure on account of their brevity, are thus developed in the nineteenth verse: "for as by the disobedience of one man many were made sinners." There is no question here of personal sins, differing in species and number, committed by each one during his life, but of one first sin which was enough to transmit equally to all men a state of sin and the title of sinners. Similarly in the twelfth verse the words "all have sinned" must mean, "all have participated in the sin of Adam", "all have contracted its stain". This interpretation too removes the seeming contradiction between the twelfth verse, "all have sinned", and the fourteenth, "who have not sinned", for in the former there is question of original sin, in the latter of personal sin. Those who say that in both cases there is question of personal sin are unable to reconcile these two verses.
IV. ORIGINAL SIN IN TRADITION
On account of a superficial resemblance between the doctrine of original sin and and the Manichaean theory of our nature being evil, the Pelagians accused the Catholics and St. Augustine of Manichaeism. For the accusation and its answer see "Contra duas epist. Pelag.", I, II, 4; V, 10; III, IX, 25; IV, III. In our own times this charge has been reiterated by several critics and historians of dogma who have been influenced by the fact that before his conversion St. Augustine was a Manichaean. They do not identify Manichaeism with the doctrine of original sin, but they say that St. Augustine, with the remains of his former Manichaean prejudices, created the doctrine of original sin unknown before his time. It is not true that the doctrine of original sin does not appear in the works of the pre-Augustinian Fathers. On the contrary, their testimony is found in special works on the subject. Nor can it be said, as Harnack maintains, that St. Augustine himself acknowledges the absence of this doctrine in the writings of the Fathers. St. Augustine invokes the testimony of eleven Fathers, Greek as well as Latin (Contra Jul., II, x, 33). Baseless also is the assertion that before St. Augustine this doctrine was unknown to the Jews and to the Christians; as we have already shown, it was taught by St. Paul. It is found in the fourth Book of Esdras, a work written by a Jew in the first century after Christ and widely read by the Christians. This book represents Adam as the author of the fall of the human race (vii, 48), as having transmitted to all his posterity the permanent infirmity, the malignity, the bad seed of sin (iii, 21, 22; iv, 30). Protestants themselves admit the doctrine of original sin in this book and others of the same period (see Sanday, "The International Critical Commentary: Romans", 134, 137; Hastings, "A Dictionary of the Bible", I, 841). It is therefore impossible to make St. Augustine, who is of a much later date, the inventor of original sin.
That this doctrine existed in Christian tradition before St. Augustine's time is shown by the practice of the Church in the baptism of children. The Pelagians held that baptism was given to children, not to remit their sin, but to make them better, to give them supernatural life, to make them adoptive sons of God, and heirs to the Kingdom of Heaven (see St. Augustine, "De peccat. meritis", I, xviii). The Catholics answered by citing the Nicene Creed, "Confiteor unum baptisma in remissiomen peccatorum". They reproached the Pelagians with introducing two baptisms, one for adults to remit sins, the other for children with no such purpose. Catholics argued, too, from the ceremonies of baptism, which suppose the child to be under the power of evil, i.e., exorcisms, abjuration of Satan made by the sponsor in the name of the child [Aug., loc. cit., xxxiv, 63; Denz., n. 140 (96)].
V. ORIGINAL SIN IN FACE OF THE OBJECTIONS FROM REASON
We do not pretend to prove the existence of original sin by arguments from reason only. St. Thomas makes use of a philosophical proof which proves the existence rather of some kind of decadence than of sin, and he considers his proof as probable only, satis probabiliter probari potest (Contra Gent., IV, lii). Many Protestants and Jansenists and some Catholics hold the doctrine of original sin to be necessary in philosophy, and the only means of solving the problem of the existence of evil. This is exaggerated and impossible to prove. It suffices to show that human reason has no serious objection against this doctrine which is founded on Revelation. The objections of Rationalists usually spring from a false concept of our dogma. They attack either the transmission of a sin or the idea of an injury inflicted on his race by the first man, of a decadence of the human race. Here we shall answer only the second category of objections, the others will be considered under a later head (VII).
(1) The law of progress is opposed to the hypothesis of a decadence. Yes, if the progress was necessarily continuous, but history proves the contrary. The line representing progress has its ups and downs, there are periods of decadence and of retrogression, and such was the period, Revelation tells us, that followed the first sin. The human race, however, began to rise again little by little, for neither intelligence nor free will had been destroyed by original sin and, consequently, there still remained the possibility of material progress, whilst in the spiritual order God did not abandon man, to whom He had promised redemption. This theory of decadence has no connexion with our Revelation. The Bible, on the contrary, shows us even spiritual progress in the people it treats of; the vocation of Abraham, the law of Moses, the mission of the Prophets, the coming of the Messias, a revelation which becomes clearer and clearer, ending in the Gospel, its diffusion amongst all nations, its fruits of holiness, and the progress of the Church.
(2) It is unjust, says another objection, that from the sin of one man should result the decadence of the whole human race. This would have weight if we took this decadence in the same sense that Luther took it, i.e. human reason incapable of understanding even moral truths, free will destroyed, the very substance of man changed into evil. But according to Catholic theology man has not lost his natural faculties: by the sin of Adam he has been deprived only of the Divine gifts to which his nature had no strict right, the complete mastery of his passions, exemption from death, sanctifying grace, the vision of God in the next life. The Creator, whose gifts were not due to the human race, had the right to bestow them on such conditions as He wished and to make their conservation depend on the fidelity of the head of the family. A prince can confer a hereditary dignity on condition that the recipient remains loyal, and that, in case of his rebelling, this dignity shall be taken from him and, in consequence, from his descendants. It is not, however, intelligible that the prince, on account of a fault committed by a father, should order the hands and feet of all the descendants of the guilty man to be cut off immediately after their birth. This comparison represents the doctrine of Luther which we in no way defend. The doctrine of the Church supposes no sensible or afflictive punishment in the next world for children who die with nothing but original sin on their souls, but only the privation of the sight of God [Denz., n. 1526 (1389)].
VI. NATURE OF ORIGINAL SIN
This is a difficult point and many systems have been invented to explain it: it will suffice to give the theological explanation now commonly received. Original sin is the privation of sanctifying grace in consequence of the sin of Adam. This solution, which is that of St. Thomas, goes back to St. Anselm and even to the traditions of the early Church, as we see by the declaration of the Second Council of Orange (A.D. 529): one man has transmitted to the whole human race not only the death of the body, which is the punishment of sin, but even sin itself, which is the death of the soul [Denz., n. 175 (145)]. As death is the privation of the principle of life, the death of the soul is the privation of sanctifying grace which according to all theologians is the principle of supernatural life. Therefore, if original sin is "the death of the soul", it is the privation of sanctifying grace.
The Council of Trent, although it did not make this solution obligatory by a definition, regarded it with favour and authorized its use (cf. Pallavicini, "Istoria del Concilio di Trento", vii-ix). Original sin is described not only as the death of the soul (Sess. V, can. ii), but as a "privation of justice that each child contracts at its conception" (Sess. VI, cap. iii). But the Council calls "justice" what we call sanctifying grace (Sess. VI), and as each child should have had personally his own justice so now after the fall he suffers his own privation of justice. We may add an argument based on the principle of St. Augustine already cited, "the deliberate sin of the first man is the cause of original sin". This principle is developed by St. Anselm: "the sin of Adam was one thing but the sin of children at their birth is quite another, the former was the cause, the latter is the effect" (De conceptu virginali, xxvi). In a child original sin is distinct from the fault of Adam, it is one of its effects. But which of these effects is it? We shall examine the several effects of Adam's fault and reject those which cannot be original sin:
Death and Suffering.- These are purely physical evils and cannot be called sin. Moreover St. Paul, and after him the councils, regarded death and original sin as two distinct things transmitted by Adam.
Concupiscence.- This rebellion of the lower appetite transmitted to us by Adam is an occasion of sin and in that sense comes nearer to moral evil. However, the occasion of a fault is not necessarily a fault, and whilst original sin is effaced by baptism concupiscence still remains in the person baptized; therefore original sin and concupiscence cannot be one and the same thing, as was held by the early Protestants (see Council of Trent, Sess. V, can. v).
The absence of sanctifying grace in the new-born child is also an effect of the first sin, for Adam, having received holiness and justice from God, lost it not only for himself but also for us (loc. cit., can. ii). If he has lost it for us we were to have received it from him at our birth with the other prerogatives of our race. Therefore the absence of sanctifying grace in a child is a real privation, it is the want of something that should have been in him according to the Divine plan. If this favour is not merely something physical but is something in the moral order, if it is holiness, its privation may be called a sin. But sanctifying grace is holiness and is so called by the Council of Trent, because holiness consists in union with God, and grace unites us intimately with God. Moral goodness consists in this that our action is according to the moral law, but grace is a deification, as the Fathers say, a perfect conformity with God who is the first rule of all morality. (See GRACE.) Sanctifying grace therefore enters into the moral order, not as an act that passes but as a permanent tendency which exists even when the subject who possesses it does not act; it is a turning towards God, conversio ad Deum. Consequently the privation of this grace, even without any other act, would be a stain, a moral deformity, a turning away from God, aversio a Deo, and this character is not found in any other effect of the fault of Adam. This privation, therefore, is the hereditary stain.
VII. HOW VOLUNTARY
"There can be no sin that is not voluntary, the learned and the ignorant admit this evident truth", writes St. Augustine (De vera relig., xiv, 27). The Church has condemned the opposite solution given by Baius [prop. xlvi, xlvii, in Denz., n. 1046 (926)]. Original sin is not an act but, as already explained, a state, a permanent privation, and this can be voluntary indirectly- just as a drunken man is deprived of his reason and incapable of using his liberty, yet it is by his free fault that he is in this state and hence his drunkenness, his privation of reason is voluntary and can be imputed to him. But how can original sin be even indirectly voluntary for a child that has never used its personal free will? Certain Protestants hold that a child on coming to the use of reason will consent to its original sin; but in reality no one ever thought of giving this consent. Besides, even before the use of reason, sin is already in the soul, according to the data of Tradition regarding the baptism of children and the sin contracted by generation. Some theosophists and spiritists admit the pre-existence of souls that have sinned in a former life which they now forget; but apart from the absurdity of this metempsychosis, it contradicts the doctrine of original sin, it substitutes a number of particular sins for the one sin of a common father transmitting sin and death to all (cf. Romans 5:12 sqq.). The whole Christian religion, says St. Augustine, may be summed up in the intervention of two men, the one to ruin us, the other to save us (De pecc. orig., xxiv). The right solution is to be sought in the free will of Adam in his sin, and this free will was ours: "we were all in Adam", says St. Ambrose, cited by St. Augustine (Opus imperf., IV, civ). St. Basil attributes to us the act of the first man: "Because we did not fast (when Adam ate the forbidden fruit) we have been turned out of the garden of Paradise" (Hom. i de jejun., iv). Earlier still is the testimony of St. Irenaeus; "In the person of the first Adam we offend God, disobeying His precept" (Haeres., V, xvi, 3).
St. Thomas thus explains this moral unity of our will with the will of Adam. "An individual can be considered either as an individual or as part of a whole, a member of a society.....Considered in the second way an act can be his although he has not done it himself, nor has it been done by his free will but by the rest of the society or by its head, the nation being considered as doing what the prince does. For a society is considered as a single man of whom the individuals are the different members (St. Paul, 1 Corinthians 12). Thus the multitude of men who receive their human nature from Adam is to be considered as a single community or rather as a single body....If the man, whose privation of original justice is due to Adam, is considered as a private person, this privation is not his `fault', for a fault is essentially voluntary. If, however, we consider him as a member of the family of Adam, as if all men were only one man, then his privation partakes of the nature of sin on account of its voluntary origin, which is the actual sin of Adam" (De Malo, iv, 1). It is this law of solidarity, admitted by common sentiment, which attributes to children a part of the shame resulting from the father's crime. It is not a personal crime, objected the Pelagians. "No", answered St. Augustine, " but it is paternal crime" (Op. imperf., I, cxlviii). Being a distinct person I am not strictly responsible for the crime of another, the act is not mine. Yet, as a member of the human family, I am supposed to have acted with its head who represented it with regard to the conservation or the loss of grace. I am, therefore, responsible for my privation of grace, taking responsibility in the largest sense of the word. This, however, is enough to make the state of privation of grace in a certain degree voluntary, and, therefore, "without absurdity it may be said to be voluntary" (St. Augustine, "Retract.", I, xiii).
Thus the principal difficulties of non-believers against the transmission of sin are answered. "Free will is essentially incommunicable." Physically, yes; morally, no; the will of the father being considered as that of his children. "It is unjust to make us responsible for an act committed before our birth." Strictly responsible, yes; responsible in a wide sense of the word, no; the crime of a father brands his yet unborn children with shame, and entails upon them a share of his own responsibility. "Your dogma makes us strictly responsible for the fault of Adam." That is a misconception of our doctrine. Our dogma does not attribute to the children of Adam any properly so-called responsibility for the act of their father, nor do we say that original sin is voluntary in the strict sense of the word. It is true that, considered as "a moral deformity", "a separation from God", as "the death of the soul", original sin is a real sin which deprives the soul of sanctifying grace. It has the same claim to be a sin as has habitual sin, which is the state in which an adult is placed by a grave and personal fault, the "stain" which St. Thomas defines as "the privation of grace" (I-II:109:7; III:87:2, ad 3), and it is from this point of view that baptism, putting an end to the privation of grace, "takes away all that is really and properly sin", for concupiscence which remains "is not really and properly sin", although its transmission was equally voluntary (Council of Trent, Sess. V, can. v.). Considered precisely as voluntary, original sin is only the shadow of sin properly so-called. According to St. Thomas (In II Sent., dist. xxv, Q. i, a. 2, ad 2um), it is not called sin in the same sense, but only in an analogous sense.
Several theologians of the seventeenth and eighteenth centuries, neglecting the importance of the privation of grace in the explanation of original sin, and explaining it only by the participation we are supposed to have in the act of Adam, exaggerate this participation. They exaggerate the idea of voluntary in original sin, thinking that it is the only way to explain how it is a sin properly so-called. Their opinion, differing from that of St. Thomas, gave rise to uncalled-for and insoluble difficulties. At present it is altogether abandoned.