Can an indulgence be applied to a deceased non-Catholic Christian?

Can an indulgence be obtained for a deceased non-Catholic Christian?

The short answer is possibly and even probably.

There are several reason, why I believe that, yes, indulgences may be applied to souls that were non-Catholic Christians in this life, but are now in purgatory and are converted.

Not wanting to politicize this question, I would simply like to bring up a certain point to start off with. Masses are offered for any number of reasons and this includes Masses being offered for the conversion of a particular Protestant of simply for their intentions. I can not tell you how many times I have read the Mass intention listed in our parish bulletin for the intentions of a certain Donald Trump. We all know the the former President of the United States is not Catholic, yet the intentions of the Sacrifice of Mass have been offered for him.

Being in purgatory presumes that non-Catholic Christians have been converted and as a result can reside in purgatory, just like Catholics.

Anne Catherine Emmerich has the following to say on the subject:

I was present when God passed sentence on notorious sinners. Great is His justice, but still more inconceivable is His mercy. He damns only those who are determined not to be converted; they who have a spark of good will are saved... I have seen in Purgatory Protestants who were pious in their ignorance; they are very desolate, for no prayers are offered for them... I saw that by our prayer and suffering, many a soul who labours not during life, can be converted and saved at the hour of death. - Purgatory for those who are saved outside the Church?

Some of these messages given to Catherine Emmerich were, 'that every parish and diocese, each city and country has its own particular and powerful guardian angel.' This Catholic mystic was to see and be told many things including these messages from Heaven, She revealed that to gain an indulgence we must approach the Sacraments with true repentance and a firm purpose of amendment or we do not gain it. She deposes that it is more holy to pray for the Poor Souls in Purgatory than for sinners who are still alive, for Anne had a particular love and devotion for the poor souls in Purgatory. She was also told that 'more Protestant souls stayed in Purgatory the longest not because they were worse than anyone else, but because so few people prayed for the repose of their souls or offered up Masses for their soul.'

Being in purgatory, means that these poor souls are converted and thus I would lean towards the possibility that an indulgence can be applied to a deceased non-Catholic Christian?

Now an indulgence can only be gained by a practicing Catholic under certain conditions. However the Church does not stipulate as to who may be the one to receive an indulgence when applied to the faithful departed when applied to the souls in purgatory.

The Gift of the Indulgence

3. To gain indulgences, whether plenary or partial, it is necessary that the faithful be in the state of grace at least at the time the indulgenced work is completed.

4. A plenary indulgence can be gained only once a day. In order to obtain it, the faithful must, in addition to being in the state of grace:

— have the interior disposition of complete detachment from sin, even venial sin;

— have sacramentally confessed their sins;

— receive the Holy Eucharist (it is certainly better to receive it while participating in Holy Mass, but for the indulgence only Holy Communion is required);

— pray for the intentions of the Supreme Pontiff.

13. Visit to a Cemetery (Coemeterii visitatio)

An indulgence, applicable only to the Souls in Purgatory, is granted to the faithful, who devoutly visit a cemetery and pray, even if only mentally, for the departed. The indulgence is plenary each day from the 1st to the 8th of November; on other days of the year it is partial. - The Enchiridion Of Indulgences

A soul in purgatory is a soul in purgatory. Nowhere does the Church define that an indulgence for particular soul in purgatory has to be named in order to receive an indulgence when we meet the requirements on their behalf. Thus the faithful may apply an indulgence to a particular member of their family, any soul in purgatory or even for the poorest soul in purgatory.

There are more ways to relieve the sufferings of the souls in purgatory than obtaining an indulgence in order to release them from their pains. Obtaining an indulgence for them is very common, especially during November. I was taught in the seminary that when we pray for a particular soul in purgatory and that that soul is no longer in need of our prayers that God will apply the merits to another soul in need. Prayer is never in vain.