COMMUNICATION IN SACRED MATTERS. - By these terms is meant the participation of Catholics in the sacred ceremonies (prayers, services, sermons, rites) performed by non-Catholics (heretics, schismatics, unbelievers) inside or outside their churches or temples. This participation can be: active, when, that is, one takes part in the religious worship positively, performing some act that has a relation to it; passive, when one takes part in it only negatively, abstaining from any action that bears a relation to the religious ceremony; formal, when there is the adherence of mind and heart; material, when this adherence is lacking and everything is reduced to an act of exterior and physical presence. Communication in sacred matters is customarily designated by the name of communicatio in divinis, to distinguish it from communicatio in profanis, that is, in private and public relations that concern domestic and civil life, and from communicatio in rebus mixtis, that is, in relations which involve acts that can be considered, or have, also a religious aspect, such as marriages, funerals and similar ceremonies.
The conduct of Catholics in this regard is regulated in principle by the CIC, and in its various applications by the norms issued by the Roman Sacred Congregations.
I. COMMUNICATIO in profanis
According to current canon law, it is lawful when there is no danger of spiritual harm; unlawful when this danger exists. Therefore those actions must also be avoided which, especially in certain determined circumstances, can signify or involve an excessive, and consequently dangerous, familiarity or confidence or intimacy with non-Catholics, especially for persons "simple and weak in the faith" (cf. Sum. Theol., 2a-2ae, q. 10, a. 9). Relations with excommunicati vitandi are regulated by particular norms (CIC, can. 2267).
II. COMMUNICATIO in divinis
It is never lawful for the faithful to assist actively or take part, in any manner, in the sacred rites of non-Catholics (CIC, can. 1258 § 1). This holds not only when it is a question of rites false or impious in themselves, but also when it is a question of those rites that are proper to this or that heretical, schismatic, pagan sect or group. For such participation is equivalent to the profession of a false religion and consequently to the denial of the Catholic faith. And even in the case where every idea of denial could be excluded, there always remain three very grave harms: 1) the danger of perversion in the Catholic who participates in it; 2) scandal, both of the faithful, who take occasion to judge badly of the person who deals with the adversaries of the faith and perhaps even to doubt its truth, and of the non-Catholics themselves, who are thus confirmed in their error; 3) indifferentism in matters of religion, that is, the exterior approval of erroneous beliefs and the idea that the external expression of one's faith is a negligible thing.
In particular: 1. Sacraments: a) Baptism: a Catholic cannot act as godparent, not even through an intermediary, in a Baptism conferred by a heretical minister, because this would be like obliging oneself to instruct or have instructed the baptized person in an erroneous doctrine (S. Uffizio, 10 May 1710; 7 July 1864; Collectan. de Prop. Fide, Rome 1907, nos. 478, 1257). b) Eucharist: a Catholic cannot assist at the Mass of a heretical or schismatic priest, even if, the precept of a holy day of obligation being urgent, he would otherwise have to remain without Mass (S. Uffizio, 7 Aug. 1704; ibid., no. 267). c) Marriage: it is not lawful to contract marriage before a heterodox minister, not even in the case of a marriage of mixed religion, nor even if one has already contracted it beforehand, or intends to contract it afterward, before a Catholic priest (CIC, can. 1065). Transgression entails excommunication reserved to the Ordinary (can. 2319). If, however, the heterodox minister acts only as an official of the State, it is lawful to make use of him, when no danger of perversion or of scandal or of contempt for ecclesiastical authority derives from it (can. 1526 § 2). d) Last Sacraments: in danger of death, when a Catholic priest is lacking, one may receive absolution from a heretical priest, on the condition that there is a probability that it will be given according to the Catholic rite (S. Uffizio, 30 June and 7 July 1864; Collectan. de Propag. Fide, no. 1257, ad 6). Furthermore: a Catholic cannot call the minister of a heterodox cult to the bedside of a dying person of the same religion so that he may administer the Sacraments to him. He may, however, have recourse to the intervention of a coreligionist of the sick person, or even himself merely inform the heterodox minister of the dying person's desire to receive a visit from him. In this second case there is nothing but an invitation similar to those that one would address to any person whatsoever, relative or friend. - 2. Other ceremonies. Catholics remain forbidden to pray, sing, play the organ in the churches and chapels of heretics and schismatics, alone or with them, while these are performing their religious functions (S. Congr. di Propag. Fide, 12 June and 8 July 1889; Collectan. de Prop. Fide, no. 1713). - 3. Public disputes. Catholics cannot take part in discussions and controversies, especially public ones, in 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 house of worship. The Ordinary can grant the use of a Catholic church for the functions of dissidents, though at hours different from the Catholic functions. Thus it happens, for example, in Abazia, Germany, Switzerland and in the church of the Holy Sepulchre in Jerusalem (S. Uffizio, 5 June 1889; CIC, Fontes, no. 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 exists a motive of honor or of civil respect; on the condition, however, that the motive be grave (approved in case of doubt by the Ordinary), that the danger of scandal or of perversion be excluded, and that no part be taken either immediately or mediately. One may therefore assist, in these cases, at the funerals, marriages and other 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 of contempt for the Catholic religion, one cannot participate in it (S. Uffizio, 11 May 1892; CIC, Fontes, no. 1154); b) in other cases one may, either for a motive of civil duty (when, for example, it is a question of one's employer, of a military leader, of the head of State); or for reasons of honor (when it is a question of a close relative, of a public benefactor, of a very intimate friend). However, in accompanying the funeral procession one cannot carry a lighted candle, nor offer suffrages for the soul of the deceased, nor sing, because these and similar acts indicate participation in the religious rite. Visiting the churches of heretics can be permitted on the ground of curiosity or study, provided it involves no intention of participating in any eventual religious rites or is not imposed by the civil authority to indicate a harmony of beliefs between Catholics and non-Catholics (S. Uffizio, 13 Jan. 1818; CIC, Fontes, no. 856).
IV. NON-CATHOLICS AND CATHOLIC RITES
Non-Catholics may receive blessings with the intention of obtaining the light of faith, or, together with this, the health of the body (CIC, can. 1149). Can. 1152, moreover, permits exorcisms to be recited over them as well. Furthermore, the Congregation of the Holy Office declared that schismatic women may sing with Catholic women in liturgical functions (24 Jan. 1906); that by way of exception non-Catholics may act as witnesses in a Catholic marriage (19 Aug. 1891); that a Protestant may temporarily act as organist in a Catholic church, provided no scandal results from it (22 Feb. 1820); that the participation of non-Catholics in Catholic worship is to be permitted only with reservation, is not to have an official character and is not to involve communion of thought with them (22 June 1859; CIC, Fontes, respectively nos. 1276, 1144, 858, 952).