St. Hermenegild was a 6th century martyr who was put to death for refusing to receive Holy Communion from his father’s Arian priest:
“During Eastertime the Arian father sent to his son a bishop of his sect, offering to receive him into his favor if he would receive Holy Communion from the hands of that prelate. St. Hermenegild refused. The father, enraged, sent soldiers to put him to death. The barbarous order was executed in 586, and St. Hermenegild died rather than renounce his Faith.” (Lives of the Saints, Rev. Hugo Hoever, p. 150.)
Some have argued that – or wondered whether – this case proves that a Catholic can never receive Communion from a heretic, including a heretical priest who purports to be Catholic and is not notorious or imposing about his heresy. If one digs into the history of St. Hermenegild’s case, the context of his refusal becomes clear, and so does the answer to our question.
St. Hermenegild was a Catholic convert who was at odds with his father. His father, Leovigild, was a radical Arian heretic. Leovigild was outraged upon learning of his son’s conversion to the Catholic Faith and was intent upon depriving Hermenegild of his kingdom and forcibly bringing him back to Arianism. The two actually went to war, with Hermenegild being imprisoned:
“It is not questioned, even by those most scornful of the idea that after his conversion Hermenegild was primarily motivated by his faith, that Leovigild now demanded his son’s return to Arianism – and was firmly refused. This known demand of 584 is further reason for believing that a similar demand had been made, rejected, and maintained from the time Leovigild first learned of his son’s conversion.” (Warren H. Carroll, A History of Christendom, Vol. 2, p. 195)
Thus, the case of Hermenegild was one where he was faced with notoriously heretical priests who were attempting to impose Arianism upon him – priests in league with his father who was trying to conquer the kingdom for Arianism. If a heretical priest demands that you accept his heretical position to receive Communion from him, you could never receive Communion from him because that would be tantamount to a silent acceptance of his heretical position. In Hermenegild’s case, reception of Holy Communion from the imposing Arian heretics would have been tantamount to an acceptance of Arianism and a denial of the Catholic Faith. Every Catholic should have resisted it even to death.
The case of Hermenegild, therefore, is obviously very different from the question of whether – in this grave crisis and necessity in which there are few valid priests left – one may lawfully receive Communion from a “traditionalist” priest (who claims to accept all Catholic teachings and celebrates the traditional Mass), but holds some heresy, such as salvation for non-Catholics, and is not notorious or imposing about his heresy. In this case, a Catholic may receive Communion and attend the traditional Mass of such a priest, as long as he doesn’t agree with him or support him at all.
Cardinal de Lugo, who was a prominent theologian of the 17th century, who was often quoted by St. Alphonsus, addresses this very issue and indicates that the position we’ve just enunciated was the common teaching of theologians.
“The second chief doubt is whether we may communicate with an undeclared heretic only in civil and human affairs or even in sacred and spiritual things. It is certain that we cannot communicate with heretics in the rites proper to a heretical sect, because this would be contrary to the precept of confessing the faith and would contain an implicit profession of error. But the question relates to sacred matters containing no error, e.g. whether it is lawful to hear Mass with a heretic, or to celebrate in his presence, or to be present while he celebrates in the Catholic rite, etc.
“But the opposite view [i.e. that attendance at such a Mass is lawful] is general [communis] and true, unless it should be illicit for some other reason on account of scandal or implicit denial of the faith, or because charity obliges one to impede the sin of the heretical minister administering unworthily where necessity does not urge. This is the teaching of Navarro and Sanchez, Suarez, Hurtado and is what I have said in speaking of the sacrament of penance and of matrimony and the other sacraments. It is also certain by virtue of the said litterae extravagantes [i.e. Ad evitanda scandala] in which communication with excommunicati tolerati is conceded to the faithful in the reception and administration of the sacraments.
“So as these heretics are not declared excommunicates or notoriously guilty of striking a cleric, there is no reason why we should be prevented from receiving the sacraments from them because of their excommunication, although on other grounds this may often be illicit unless necessity excuse as I have explained in the said places.” (Cardinal John de Lugo S.J. (1583-1660), Tractatus de Virtute Fidei Divinae: Disputatio XXII, Sectio . According to The Catholic Encyclopedia, St. Alphonsus regarded Cardinal de Lugo as second only to St. Thomas as a theologian.)
Notice that Cardinal de Lugo distinguishes between attending a heretical rite (which is never permitted) and attending a Catholic Mass or rite celebrated by an undeclared heretic (e.g. a priest of the SSPX who celebrates the Catholic rite and claims to be Catholic but is actually a heretic). De Lugo is thus addressing the very issue which is confronting people today and which was posed in the question. And what does he say? He teaches that attendance at such a Mass is lawful and that this is the “general and true” position of Catholic theologians. Please note that Cardinal de Lugo also points out that if circumstances are such that scandal or a denial of the Faith would necessarily arise (e.g., if the priest made an announcement that everyone who attends must agree with him, such as the priests of the SSPV have on the salvation issue), then you necessarily couldn’t go; or if the priest is notorious about his heresy, then you definitely shouldn’t go.