(b) It is not lawful to accept a false certificate of participation in false worship. Hence, the early Church condemned as apostates the Libellatics (i.e., those Christians, who, to protect themselves in time of persecution, obtained by bribery or otherwise a forged or genuine magistrate’s certificate that they had sacrificed to the heathen gods).
966. It is unlawful for Catholics to assist passively at non-Catholic worship, unless there are present the conditions requisite for performing an act that has two results, one good and the other evil (see 104); for even passive assistance frequently involves sin.
(a) Hence, the assistance itself must be really indifferent, that is, it must be a merely passive presence without any active participation in the service. Examples: A person who stands in the rear of a Quaker meeting house as an onlooker assists passively; but one who sits quietly among the others present, as if in meditation, assists actively. A person who sits in a pew during a revival in order to see what is going on, assists passively; but, if he joins with the congregation in bowing, groaning, etc., he assists actively.
(b) The evil effect that may result from assistance (such as scandal and danger of perversion) must not be prior to the good effect; otherwise, evil would be done for the sake of good. Examples: Titus, a non-Catholic, goes to Mass as a spectator, with his Catholic friend Balbus. He then asks Balbus to assist as a spectator at the services of his denomination, and thus see for himself that the latter is better. Balbus, in order to be courteous, consents. Here Balbus aims to show politeness, which is good, but the means he uses—namely, the impression he gives that he is not convinced of the superiority of his own religion—is bad.
(c) The evil effect (i.e., remote danger of perversion, unavoidable scandal) must not be intended or approved, but only permitted. Example: Caius, a Catholic public official, has to attend funerals and weddings in Protestant churches as a mark of the public respect for notable persons. He knows that a few will take scandal at his action, but he wishes only to do his duty as an official, and not to offend anyone (see on Scandal).
(d) The cause of assistance must be in proportion to the kind of assistance. Hence, a greater reason is required for assistance on several occasions than on one, for assistance at infidel than at heretical services, for assistance at the primary than at the secondary act of worship, for assistance by a priest than for assistance by a layman, etc. Example: Graver reason would be necessary to justify assistance at a non-Catholic funeral, if there were signs of anti-Catholicism manifested (e.g., flower designs and regalia of a hostile sect placed on the coffin), than if the service contained nothing offensive.
967. Cases of communication in false sacrificial rites are as follows: (a) Active participation is had in such acts as the slaying and offering of victims, the burning of incense before idols, the eating of sacrificial banquets; (b) Passive participation is had when one merely watches the rite of sacrifice without taking any part therein.
968. Cases of communication in the Sacrifice of the Mass are as follows: (a) Active participation is had in such acts as taking the part of deacon in a schismatical Mass, assisting at a schismatical Mass with the intention of hearing Mass formally (i.e., of offering it with the priest). If on Sunday, one is where there is only a schismatical church, one is excused from the obligation of hearing Mass, and may not hear Mass in that church (Holy Office, December 5, 1608; August 7, 1704). (b) Passive participation is had when one is present merely as a spectator, kneeling before the Blessed Sacrament, but giving no other signs of religious devotion. This is permissible under the conditions mentioned above (see 966), if there is no scandal, or danger of perversion (Holy Office, April 24, 1894).
969. Cases of participation in the Sacraments or sacramentals, real or reputed, are as follows: (a) Active participation takes place when one receives a Sacrament from a non-Catholic minister, or offers one’s child to receive a Sacrament from such a minister, or contracts marriage in the presence of such a minister, or acts as sponsor at a non-Catholic baptism or confirmation or as the religious witness at a non-Catholic marriage, or answers in public non-Catholic prayers, or takes ashes blessed by schismatics. (b) Passive participation is had when one merely looks on at the administration of a Sacrament or sacramental by a non-Catholic minister, without signs of approval or union in what is being done.
970. There are certain cases that seem to be active participations in Sacraments with non-Catholics, and yet are permitted by the Code. In reality, however, there is no active communication in those cases.