**COMMUNICATION IN SACRED MATTERS** — By this term is understood the participation of Catholics in sacred ceremonies (prayers, services, sermons, rites) performed by non-Catholics (heretics, schismatics, infidels) inside or outside their churches or temples. This participation may be: active, when one positively takes part in the religious worship by performing some act connected with it; passive, when one merely takes part in a negative way by abstaining from any action that would imply a connection with the religious ceremony; formal, when there is an adherence of the mind and heart; material, when this adherence is lacking and everything reduces to an external and physical presence.
Communication in sacred matters is usually designated by the term *communicatio in divinis*, to distinguish it from *communicatio in profanis*, i.e., in private and public relations concerning domestic and civil life, and from *communicatio in rebus mixtis*, i.e., in relations which involve acts that may be considered or have a religious aspect, such as marriages, funerals, and similar ceremonies.
The conduct of Catholics in this regard is regulated in principle by the *Codex Iuris Canonici* (CIC), and in its various applications by the norms issued by the Roman Congregations.
I. *Communicatio in profanis.* — According to current canon law, it is lawful when there is no danger of spiritual harm; unlawful when such danger exists. Therefore, even those actions which, especially in certain circumstances, may signify or imply an excessive familiarity, confidence, or intimacy—and consequently be dangerous—with non-Catholics must be avoided, particularly in the case of persons “simple and weak in faith” (cf. *Summa Theologica*, II-II, q. 10, a. 9). Relations with excommunicated persons to be avoided (*vitandi*) are governed by special norms (CIC, can. 2267).
II. *Communicatio in divinis.* — It is never lawful for the faithful to assist actively or take part in any way in the sacred rites of non-Catholics (CIC, can. 1258 § 1). This applies not only when the rites are false or impious in themselves, but also when they are rites proper to this or that heretical, schismatic, or pagan sect. For such participation is equivalent to a profession of a false religion and consequently to a denial of the Catholic faith. Even if the idea of denial could be excluded, there remain three very serious dangers: 1) the danger of perversion for the Catholic who participates; 2) scandal, both for the faithful, who may take occasion to judge unfavorably the person who associates with the adversaries of the faith and perhaps even to doubt the truth of the faith, and for the non-Catholics themselves, who are thus confirmed in their error; 3) religious indifferentism, i.e., the outward approval of erroneous beliefs and the idea that the external expression of one’s own faith is a matter of little importance.
In particular: 1. Sacraments: a) Baptism: a Catholic may not act as godparent, even through an intermediary, at a Baptism administered by a heretical minister, because this would be tantamount to obliging oneself to instruct or have the baptized instructed in erroneous doctrine (*Holy Office*, 10 May 1710; 7 July 1864; *Collectanea S. Congregationis de Propaganda Fide*, Rome 1907, nn. 478, 1257). b) Eucharist: a Catholic may not attend the Mass of a heretical or schismatic priest, even if, in the absence of other means, the precept of attending Mass on Sundays and holy days would otherwise remain unfulfilled (*Holy Office*, 7 Aug. 1704; *Collectanea*, n. 267). c) Marriage: it is not lawful to contract marriage before a heterodox minister, even in the case of a mixed marriage, nor even if the marriage has already been contracted or is intended to be contracted afterwards before a Catholic priest (CIC, can. 1063). Transgression incurs the censure reserved to the Ordinary (can. 2319). If, however, the heterodox minister acts merely as a civil official, it is lawful to make use of him, provided that no danger of perversion, scandal, or contempt for ecclesiastical authority arises (can. 1526 § 2). d) Last Sacraments: in danger of death, lacking a Catholic priest, one may receive absolution from a heretical priest, on the condition that there is a probability that it will be administered according to the Catholic rite (*Holy Office*, 30 June and 7 July 1864; *Collectanea*, n. 1257, ad 6). Furthermore: a Catholic may not call upon the minister of a heterodox cult to administer the Sacraments to a dying person of the same religion. However, one may resort to the intervention of a fellow believer of the sick person, or even merely inform the heterodox minister of the dying person’s wish to receive a visit. In this latter case, one is merely extending an invitation similar to that which would be offered to any other person, relative, or friend. — 2. Other ceremonies: Catholics are forbidden to pray, sing, or play the organ in the churches and chapels of heretics and schismatics, whether alone or with them, while they are performing their religious services (*S. Congregation of Propaganda Fide*, 12 June and 8 July 1889; *Collectanea*, n. 1713). — 3. Public disputes: Catholics may not take part in discussions and controversies, especially public ones, on matters of faith with non-Catholics, without the permission of the Holy See, or, in urgent cases, of the Ordinary (CIC, can. 1325 § 3). — 4. Common use of a church: The Ordinary may grant the use of a Catholic church for the services of dissidents, but at times different from Catholic services. This occurs, for example, in Alsace, Germany, Switzerland, and in the church of the Holy Sepulchre in Jerusalem (*Holy Office*, 5 June 1889; *CIC, Fontes*, n. 1119).
III. *Communicatio in rebus mixtis.* — Purely passive presence or participation in the ceremonies of a non-Catholic cult is tolerated by the Church when there is a motive of honor or civil respect; provided, however, that the motive is grave (approved in case of doubt by the Ordinary), that there is no danger of scandal or perversion, and that no part, whether direct or indirect, is taken in the ceremony. Therefore, one may attend, in such cases, the funerals, marriages, and similar ceremonies of non-Catholics (CIC, can. 1258 § 2).
Thus, in the case of funerals: a) if the funeral is organized as a manifestation of unbelief or contempt for the Catholic religion, one may not participate (*Holy Office*, 11 May 1892; *CIC, Fontes*, n. 1154); b) in other cases, one may attend either for reasons of civil duty (e.g., when it concerns an employer, a military commander, or the head of state) or for reasons of honor (e.g., when it concerns a close relative, a public benefactor, or a very intimate friend). However, when accompanying the funeral procession, one may not carry a lighted candle, nor offer suffrages for the soul of the deceased, nor sing, because such and similar acts indicate participation in the religious rite. Visiting the churches of heretics may be permitted out of curiosity or for study, provided that it does not involve any intention of participating in any religious rites that may be taking place there, nor is it imposed by civil authority to indicate a harmony of beliefs between Catholics and non-Cathol