Nothing like Thomistic training to make a teacher present clear ideas.
Commentary will be later in the day.
OBSESSION
Obsession is a series of temptations that are more violent and prolonged than ordinary temptations. Rarely does the devil act only on the exterior senses; more frequently, through the imagination; he provokes lively impressions of the sensible appetites in order to trouble the soul. He may act on the sight by loathsome apparitions or, on the contrary, seductive apparitions; (4) on the hearing, by making a racket (5) or by making the person hear blasphemous or obscene words; (6) on the touch, by inflicting blows or by embraces of a nature to lead to evil.(7) There are cases in which these apparitions are not corporeal, but imaginary or produced, like hallucination, by nervous overexcitement.
The direct action of the devil on the imagination, memory, and passions, may produce obsessing images, which persist in spite of energetic efforts and which lead to anger, to very lively antipathies, or to dangerous affections, or again to discouragement accompanied by anguish. Those whom the enemy of good persecutes in this way feel at times that their imagination is as if bound by thick shadows, and that over their heart rests a weight which oppresses them. This powerlessness is entirely different from that proceeding from the divine action which, in bestowing infused contemplation, renders discursive meditation more or less impracticable. The enemy of God, in his jealous desire to imitate the divine action, seeks to cause the effect of God's action to deviate, in such a way that, in the passive purifications, the soul occasionally finds itself between the special action of God, which inclines it to a spiritual life more freed from the senses, and an inverse action, which in its way strikes it with powerlessness in order to cause the effect of the divine action to deviate and to throw the soul into utter confusion.
If the temptations of which we are speaking are sudden, violent, and persistent, and no illness explains them, a special influence of the devil may be seen in them.
Obsession may be so strong that it deserves the name of diabolical siege. Scaramelli says: "In the diabolical siege, the devil stays near the person whom he besieges as a captain does near a place which he surrounds closely with his troops. But he has no stable and permanent power over the body of the obsessed person (which occurs only in possession); and once the time of purification is ended, the devil himself raises the siege and goes off without exorcisms, without injunction." (8)
By what sign may one recognize that obsession is related to the passive purification of the senses? Obsession may be linked with the passive purification of the senses if the obsessed person works seriously at his perfection, in particular if he is humble, obedient, charitable, and if he has the three signs of the night of the senses indicated by St. John of the Cross. On the other hand, astute, very subtle persons may, for interested motives, seek to make themselves pass for victims of the devil, in such a way especially as to excuse excessively compromising exterior faults which they commit.