HERESY. - Greek word (αἴρεσις), meaning "choice," "election."
I. GENERAL NOTIONS
The term, quite frequent in profane usage, originally served above all to indicate the preference for a given religious, philosophical or political doctrine, then the followers of that doctrine and finally the doctrine itself, without however including any note of reproach or condemnation. In the New Testament, where it occurs 9 times, it is used in the sense of a sect or doctrine to be rejected: thus St. Paul rejects the title of heresy applied by the Jews to nascent Christianity (Acts 24:14).

The Apostolic Fathers, the apologists and especially Tertullian (De Praescr., 6) further clarify its meaning, branding as heretics all those who wish to introduce a personal variation within Christianity in contrast with the traditional teaching of the Church. Finally, with St. Jerome the term was used only to indicate groups separated from the Church for false doctrines, while the detachment for refusal of obedience to the hierarchy was called schism: « Inter haeresim et schisma hoc arbitrari interesso, quod haeresis perversum dogma habeat, schisma autem quod ab Ecclesia separet » (In Epist. ad Titum: PL 26, 508). It thus remains established that in heresy a doctrinal dissent prevails, in schism a disciplinary dissent. Terms and concept, elaborated in this way by the Fathers, passed into subsequent ecclesiastical usage.
Heresy presents many problems for theology, to be examined by considering its dogmatic, moral, canonical and historical aspects.
II. IN DOGMATICS: HERESY-AS-DOCTRINE
Objectively considered, heresy can be defined as: « a doctrine that directly contradicts a revealed truth » as such proposed by the Church to the faithful. A threefold element thus comes into play: 1. A revealed truth, contained either implicitly or explicitly, but formally in at least one of the two sources of Revelation. Therefore neither the truths deduced from revealed principles by means of a premise of a natural order (theological conclusions), nor those philosophical truths or those facts that are intimately and necessarily connected with the declaration and the security of Revelation itself, can constitute the matter of heresy. Such truths and facts do indeed fall within the orbit of the Church's infallibility, from which they could also receive absolute certainty and immutability, but they do not for this reason become revealed, that is, to be believed on the authority of God or, as is usually said, with divine faith. 2. An intervention of the infallible magisterium of the Church that attests the revealed character of the doctrine, whereby what was previously only the object of divine faith comes to assume the qualification of a truth to be believed by divine and catholic faith. 3) An opposition to the revealed truth; and such opposition must be immediate, direct and contradictory.
If one of these elements is lacking, a proposition cannot properly be called heretical, but, according to the circumstances, it will be called: proximate to heresy, if it contradicts a doctrine proximate to the faith, that is, one which, although not yet defined, is considered by theologians as definable: erroneous, if it denies a theological conclusion or in general a truth intimately connected with dogma; sapiens haeresim, if the form of the expression in certain circumstances generates suspicion of heresy (v. CENSURA).
III. IN MORALS: HERESY-AS-SIN
St. Thomas reduces it to a species of positive infidelity (Sum. Theol., 2ᵃ — 2ᵃᵉ, q. 11, a. 1). Therefore as a sin it is usually defined as: «the voluntary and pertinacious error of a Christian against a divine-catholic truth».
It is said: 1. Voluntary error. The sin of heresy, in fact, corresponding in a contrary sense to the act of faith, is first of all an act of the intellect constituted by an erroneous judgment against the rule of faith. It can manifest itself in a denial or even in a positive doubt that reduces certainty to mere opinion. Negative doubt, which is limited to a suspension of judgment, although it can be gravely sinful, is not yet directly opposed to faith. Positive doubt, on the other hand, precisely because it weakens adherence to the teaching of the Church, is already a formal revolt against faith itself, which requires a firm and unshakable assent. Besides the intellectual element, an impulse on the part of the will also intervenes in the genesis of heresy, analogously to what happens in the act of faith: only through such influence, in fact, is it explained how the intellect can freely determine itself to give its erroneous assent concerning Revelation. 2. Pertinacious. This pertinacity constitutes the specific element of its moral culpability. It does not consist in a special obstinacy, but in the awareness that one has of opposing the rule of faith, so that, this being lacking, the heresy will be purely material, not formal. 3. Of a Christian, whereby the capable subject can only be one who through Baptism has entered to become part of the ecclesiastical society: the catechumen, therefore, or one who has been invalidly baptized, will be able to commit the sin of infidelity, not of heresy. 4. Against a truth, etc. These words refer to the objective element already treated above.
The sin of heresy is subdivided into: 1. formal and material, according to whether or not it is joined with pertinacity; 2. internal and external, according to whether it resides only in the mind or also manifests itself externally; 3. occult and public, according to whether it is manifested to no one or to few and in secret, or before a considerable number of persons.
Among the sins of infidelity it is the most grave, because more than any other it is opposed to the virtue of faith: indeed, by such opposition it surpasses the gravity of any sin, with the exception of hatred against God. Such gravity is reflected in the many consequences that come to strike the heretic in his relations with the interior Christian life and with ecclesiastical society. The most important are: 1. the loss of the life of Grace; 2. the destruction of the infused virtue of faith; 3. the separation from the body of the Church in the case of public heresy, whereby the heretic comes to constitute himself a torn-away and separated member, even if, as the more common doctrine holds, he adheres to heresy only materially. It is not certain that the same can be said of the occult heretic, that is, of one who has not yet officially professed himself as such.
IV. IN CANON LAW: HERESY-AS-DELICT
Heresy, insofar as it breaks the unity of the Church, is by its nature an eminently antisocial fact: it cannot therefore escape the coercive power of the same. However grave it may be with regard to doctrine and morals, the sin of heresy, if it remains a purely internal fact, does not yet constitute a delict in the juridical sense of the word, and thus liable to canonical sanctions. To become such, it is necessary that heresy also assume an external character, whether public or occult. Such external manifestation can express itself in any manner, with signs, writings, words and actions, provided it results sufficiently that it is a true and proper adherence, and moreover fully deliberate, that is, formal.
Varied was the manner used over the centuries by the Church in the repression of heresy. Most severe at first, later it somewhat tempered the primitive rigor, while still reserving very heavy penances for such a delict. Once the Empire became Christian, civil sanctions such as exile, confiscation of goods and even death were added to the ecclesiastical penalties. Particularly harsh was the struggle against heretics after the year 1000, due to the rise of new heretical movements. The institution of the Inquisition (v.) dates back to this period.
The penalties today in force are the following (can. 2314 of the CIC): 1. Heretics incur ipso facto excommunication. 2. If admonished they do not repent, they shall be deprived of benefices, dignities, pensions, offices and other ecclesiastical charges; they shall be declared infamous and, if clerics, after a second admonition, deposed. 3. Those enrolled in or publicly adhering to non-catholic sects are for that very reason infamous, and, if clerics, after having been admonished in vain, must be degraded.
To one who is suspected of heresy, admonished in vain, legitimate ecclesiastical acts shall be forbidden, and, if a cleric, he shall be suspended a divinis; if within 6 months he does not amend, he shall be considered a heretic (can. 2315).
Absolution from the excommunication is reserved to the Apostolic See; if, however, the offense was referred to the Ordinary in the external forum, even by free confession, the latter, after an abjuration (v.), can absolve the offender in the external forum; the latter may then receive absolution from the sin from the confessor (can. 2314 § 2).

V. IN THE HISTORY OF THE CHURCH
The breadth of the theme allows only a mention of the major heretical movements, for which reference is made to the relevant entries.
1. Patristic period
Heresy appears with the very rise of the Church. The first manifestations come from the Jewish milieu, through the work of groups that passed over to Christianity without, however, definitively detaching themselves from the Synagogue: the Ebionites, the Nazarenes, the Cerinthians belong to this category. An analogous movement came to arise among the pagan milieu in the 2nd century with Gnosticism: it in fact represents the attempt on the part of pagan thought to absorb and adulterate the Gospel doctrine, transforming it into a religious philosophy. Marcionism, millenarianism, Manichaeism are so many heresies, arisen through contamination with other religions. On a clearly Christian basis, however, Montanism arose in the 3rd century, with the proclamation of the third and final Revelation, that of the Holy Spirit. The controversies against the heretics, together with the penetration of the Gospel among the educated classes, meanwhile open a new series of heresies of a predominantly intellectual character, which will lead successively to the denial of the most fundamental dogmas. It was the Trinitarian doctrine that was first denied between the 2nd and 3rd centuries, both in the East with subordinationism and in the West with the monarchianism of Noetus and Praxeas, later developed in Sabellian modalism: errors which at the beginning of the 4th century would issue in Arianism, denier of the divinity of the Word, which would be followed by Macedonianism, a heresy analogous with regard to the Holy Spirit.
Once the Trinitarian controversies ceased, the struggle was rekindled in the East between the 5th and 6th centuries on christological ground. Nestorianism, which denied the unity of person in Christ, Monophysitism, which confused His natures, and later Monothelitism, form the most important deviations in this field. The West meanwhile was becoming impassioned over the problems concerning the Church, the Sacraments, and Grace: hence Donatism and above all Pelagianism, both vigorously combated by St. Augustine. Iconoclasm represents the last great heresy of this tormented patristic period, which nevertheless had a decisive importance in the precise formulation of dogma.
2. Early Middle Ages
In the period following that of the Fathers, worthy of note are the Adoptionism of Elipandus of Toledo and Felix of Urgel and the predestinarianism of Gottschalk. At this time too the Greek schism takes its place: at least in its beginnings, however, it did not involve particular heretical affirmations. Of quite another nature, instead, are the dangers that the Church had to face after the year 1000. Popular movements of reform and of a clearly anarchic and anti-ecclesiastical character swarmed everywhere. The Cathars, the Waldensians, then the pseudo-mystical currents of the Joachimites, the Fraticelli and the Beghards are the most significant expression of this heretical ferment. Even the constitution of the Church is subsequently undermined by the doctrine of Marsilius of Padua and by the so-called conciliar theories. When later the movements of the Englishman Wycliff and the Bohemian Hus are added, the ground will already be ready for the outbreak of the Lutheran revolt.
3. Modern age
The modern period opens with Protestantism, which broke the unity of the Church of the West and led the life and culture of Europe to a gradual detachment from Christianity. New trials await the Church in the 18th century. The Reformation had in fact given occasion for most serious controversies concerning Grace and freedom, from which movements were born that, while professing themselves orthodox, were practically rebellious against dogma and the hierarchy, such as Baianism and above all Jansenism, the latter a heresy of exceptional importance, whose resonances reach as far as the 20th century. Meanwhile, on juridical ground, the intensifying of nationalism and of the absolutism of sovereigns provokes Gallicanism, Febronianism, Josephinism, which place the Church in grave difficulty in its relations with the State. Noteworthy in this period are also the controversies in the moral field, which determined the condemnation of laxism, rigorism and quietism. In the 19th century, on the other hand, traditionalism, fideism, ontologism, Hermesianism, Güntherianism, the "Old Catholics" had wide resonance in France and Germany. The other errors against which the Church in this century must above all defend itself are, more than heresies, forms of total defection from Christianity. The last grave attack has been the more recent one of Modernism, with which an attempt was made to introduce rationalism into the field of theology and biblical criticism.
Bibliography8 works
For morals: St. Thomas, Suarez, De Lugo cited above and above all St. Alphonsus de' Liguori, Theologia moralis, I, ed. Gaude, Rome 1907, p. 310 ff., where many references to previous authors are found. Besides the classic texts of D'Annibale, Bucceroni, Ballerini, Lehmkuhl, among recent ones especially A. Vermeersch, Theologiae moralis principia, II, 3rd ed., Rome 1937, pp. 22 ff.; D. and M. Prümmer, Manuale theologiae moralis, I, 6th ed., Freiburg im Br. 1940, pp. 364 ff.; J. Aertnys-C. Damen, Theologia moralis, I, 14th ed., Turin 1947, pp. 267 ff.
For canon law: as regards works prior to the CIC reference is made to Michel, op. cit. Among the commentators on the CIC see F. Cappello, De censuris, Turin 1916, passim; E. F. Mackenzie, The delicts of heresy, Washington 1932; G. Chelodi, Ius poenale, 4th ed., Trent 1935, p. 75 ff.; M. Conte a Coronata, Institutiones I. C., II, 8th ed., Turin 1939, p. 247 ff.; and IV, ibid. 1935, p. 279 ff.; G. Chelodi-P. Ciprotti, Ius Canonicum de delictis et poenis, 5th ed., Vicenza 1943, pp. 75-80.
For history: the decisions of the Church against the various heresies are collected in Denz-U. For the authors who collected the heresies in corpus cf. J. Hermant, Histoire des hérésies, Rouen 1712; G. Arnold, Unparteyische Kirchenund Ketzerhistorie, Frankfurt am Main 1729; F. Van Ranst, Historia haereticorum et haeresium, Venice 1735; W. Walch, Entwurf einer vollständigen Geschichte des Ketzereins, Leipzig 1769; C. Cantù, Gli eretici in Italia, Turin 1865-67; A. Lombardi, Pauliciens, bulgares et bons-hommes en Orient et Occident, Basel 1870; F. Tocco, L'eresia nel medioevo, Florence 1884 (tendentious); J. Döllinger, Beiträge zur Sektengeschichte des Mittelalters, Munich 1890; G. Volpe, Movimenti religiosi e sette ereticali nella società medioevale italiana, 2nd ed., Florence 1926. Among the various dictionaries of heresies see Ph. Fritz, Ketzerlexikon, Rathbone 1858; F. A. Pouget and J. Claris, Dictionnaire des hérésies, in J. P. Migne, Encyclopédie théologique, XI and XII, Paris 1847; J. H. Blunt, Dictionary of sects and heresies, London 1903; G. Runciman, Le manichéisme médiéval, L'hérésie dualiste dans le christianisme, French trans., Paris 1948; H. Jedin, Storia del Concilio di Trento, Italian trans., Brescia 1950; P. Havait, Les délits d'hérésie d'apostasie et de schisme, in Revue d'ascétique et de mystique de Tournai, 5 (1930), pp. 134-39; G. Welter, Hist. des sectes chrétiennes des origines à nos jours, Paris 1922 (the author is non-Catholic).
VI. ARCHAEOLOGY
If by this word we are to understand a system or a doctrine, and consequently a sect that rejects a part of the Church's teaching, then very few are the products of art whose heterodox character can be demonstrated and defined with certainty. Christian-heretical scenes must not be confused with those of purely pagan origin, even if tinged with mystical reflections that may have some connection with Christianity.
Setting aside, because of its rather magical character, the numerous collection of amulets and gems of which the Gnostics made wide use, a few monuments of the so-called major arts are known, which in their decoration reveal more or less evident mixtures of purely Christian motifs with others more mysterious, which seem to have to be attributed to heterodox speculations. The most typical case is constituted by the hypogeum of the Aurelii on Viale Manzoni, without, however, the interpreters having been able to agree in determining the sect that used it: Gnostic, Carpocratian, Marcionite, Montanist?
The heretical character of the so-called hypogeum of Trebius Justus on the Via Latina is very doubtful. The same should be said of the representations discovered beneath the basilica "in catacumbas."
Two sarcophagi of the Museo delle Terme were attributed by Wilpert to Gnostic patrons: one would represent Simon Magus instructing Helena, the other Christ as teacher between James the Less and Mary Magdalene; his arguments, however, are not entirely convincing.
Also with regard to epigraphy, inscriptions have been held to be heretical by Cecchelli and by Calder which Ferrua, on the other hand, did not admit as such.
Bibliography4 works
Luciano De Bruyne