Some people object to the idea of "heresy by omission" – and this objection is especially mounted by defenders of the Novus Ordo rites and the documents of Vatican II.
Fr Raffaele Pierotti OP was Master of the Sacred Palace and papal theologian under Pope Leo XIII. In 1896, the Pope assigned him the task of summarising the papers of the Papal Commission on the question of Anglican Orders. The "painstakingly fair summary" in his "Votum and Report" was essentially the final step before Pope Leo XIII issued Apostolicae Curae.
Some defenders of the validity of the Anglican rite had argued that the Anglican rite only conveyed error by omission, and that therefore a Catholic form used in such a rite would retain its Catholic meaning (and thus, they would argue, be sufficient for validity).
Here is what Fr Pierotti made of this argument:
"I must now add a few words about the replies given to this question by the defenders of validity or doubtful validity. Gasparri replied that in the new ritual heresies are not expressed positively but only negatively, and therefore the heretical doctrine of the compilers is not clearly expressed in it.
"To this I reply that there are sins both of commission and of omission, and that in order to call a rite heretical, it is not necessary that heresy be positively professed in it, when the Catholic dogma has been removed from it, nor does it follow that the dogma has to be denied.
"For example, to render the form of Baptism invalid, it is not necessary that there be in it an explicit denial of the existence or divinity of the Holy Spirit; it would be enough to omit the mention of this third divine Person, precisely in the way that the compilers of the Ordinal have acted in omitting the mention of the order or the power that is being conferred.
"By this they have said clearly enough that they do not believe in the existence of the Sacrament of Orders."
In other words, it is possible to profess heresy "negatively" by omission, as well as "positively".
This has implications for the documents of Vatican II – as
@FrDesposito is arguing in thread from which the quote tweet is taken – as well as for the Novus Ordo rites themselves.
Defenders of both claim that they do not contain positive expressions of error or heresy – but even if this was conceded, the fact that the documents were composed and the rites were mutilated in order to please the world and non-Catholics is sufficient to convey the belief of those who framed them.
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With thanks to the friend who drew our attention to this document, which is found in Anglican Orders: The Documents in the Debate, p 254-5, ed. Christopher Hill & Edward Yarnold SJ, Canterbury Press, 1997, (n. 54 of the Votum and Report of Fr Pierotti)
By omitting the explicit scholastic definition of the Two Sources, the Council created a dangerous ambiguity. This is "heresy by omission"—failing to teach a defined truth of the Faith in order to establish a false ecumenism with Protestantism.