Dear Omar:

Well, first off, the quote from Father Sinistrari is a misquote. The source of this quote on Wikipedia is Fallen Angels and Spirits of The Dark by Robert Masello. Either Mr. Masello misquoted Father Sinistrari, or the author of the Wikipedia article misquoted Masello.

In the quote there are two whole phrases missing in between "Incubi..." and "...do not obey". Removing these phrases completely changes the message given by Father, and makes it look like Father is saying something he is not.

Father is not saying that incubi, as a class of demons, do not obey exorcists. Here is the actual quote, in context:

Et quod mirum est, et pene incapabile, tales Incubi, qui Italice vocantur FoUetti, Hispanice Duendes, Gallice Follets, nee Exorcistis obediunt, nee exorcismos parent, nee res sacras reverentur ad earum approximationem timorem astendendo.

A most marvellous and well high incomprehensible fact : the Incubi whom the Italians call Folletti, the Spaniards Duendes, the French Follets, do not obey the Exorcists, have no dread of exorcisms, no reverence for holy things, at the approach of which they are not in the least overawed;

Father is speaking about a specific demon called "Folletti," not all incubus as the misquote implies.

There are demons who are stronger than other demons. Some demons are much harder to exorcise than others. It is also true that solemn exorcism seems to fail in some cases with some victims. Of course, no demon can resist God, but God does, for whatever reasons, seem to allow some demons to resist all attempts to expel it. So, yes, there can be demons who can ignore and be unaffected by the exorcist's commands.

The Church, to my knowledge does not officially categorize demons beyond the categorizations and names mentioned in the Bible (e.g., St. Paul's suggestion of demon hierarchy in Ephesians 6:12, names such as Lucifer, Satan, Legion in Mark 5:9, spirit of infirmity in Luke 13:11, etc.).

Most information of such kind comes from the writings of Saints, and the clinical experience and writings of exorcists. As such, we cannot know the full extent of demon hierarchy, structure of society, or types and kinds.

The types labeled incubi and succubi are terms sourced in the 14th century Middle Ages to describe demons with certain characteristics of behavior and effects upon humans. Thus, the term is a term of attributes of demonic activity not unlike saying, the demon of lust, of anger, or suicide, etc. Since the Church does not allow us to ask demons for their actual names, we can refer to demons by their attributes. Incubi and succubi are really just that—referring to demons by their attributes.

By the way, I have dealt with incubus and succubus and have successfully commanded it, at least in part, but these particular sexual demons are very tenacious.

God Bless,
Bro. Ignatius Mary