In his July 3 Outlook essay, “As a psychiatrist, I diagnose mental illness. Also, I help spot demonic possession,” Richard Gallagher cited as evidence that a woman was possessed by a demon the fact that “she could tell some people their secret weaknesses, such as undue pride.” If that impressed Gallagher, he should read a horoscope sometime. That vague and overly general “secret” is a simple cold reading technique; a cheap parlor trick that a self-described “man of science” shouldn’t be so naive about. Regardless, Gallagher made quite a leap from phenomena he couldn’t explain to his conclusion that the patient must be possessed by a demon. How does he know they aren’t being haunted by leprechauns or possessed by the ghost of Elvis Presley?

People, including children, have been murdered by their relatives based on suspicions of demonic possession. For The Post to legitimize such a nonsensical belief in the pages of its paper is the height of irresponsibility.

Andrew Walko, Springfield

In his defense of demonic possession as a real phenomenon, Richard Gallagher demonstrated how one can be both a “man of science” and a very sloppy thinker.

There were two philosophical flaws in his essay.

He made a hasty leap from “cannot be explained except by special psychic or preternatural ability” to “demonic possession.” In so doing, he overlooked myriad alternate (non-“demonic”) scenarios that might fully account for the phenomena he observed. For instance, the “hidden knowledge” (say, speaking Latin) that a “possessed individual” displayed might well be the result of telepathic functioning among living individuals (who speak Latin) and have nothing at all to do with “demons.” This is a lively topic of discussion among contemporary philosophers of the paranormal. Gallagher seemedunaware of it.

Gallagher committed a category error in drawing an analogy between the evidence for demonic possession and that for George Washington crossing the Delaware. The latter is an empirical matter, while the former raises difficult conceptual issues. How can an entity that is purely spiritual (and therefore non-spatial) “possess” a human body? Gallagher demonstrated no awareness of this issue, which has troubled philosophers at least since the time of Descartes.

The astute reader will not let Gallagher’s Ivy League education mask the fact that he simply has not done his philosophical homework.

Steve Baughman, San Francisco

Demonic attacks exist in the practice of Richard Gallagher. He will try to sell a book describing his personal management of the syndrome of demonic possession. As a “man of science,” a psychiatrist, Gallagher is supposed to understand that there should be a reasonable number of demonic possessions and an equal number of control patients without demonic possession to establish clinical fact. It takes a lot more than “personal observation,” Mia Farrow and priestly belief to establish a clinical medical disease.

Psychiatry has a long and troubled scientific history with such concepts involving Oedipus, female genital envy and infantile sexual desires. Those of us who have endured generations of questionable science in the psychiatric profession shudder at this continued onslaught. The catechism of “sentient demons” did little to impress me that psychiatry is making scientific progress.

I am overjoyed that George Washington did indeed cross the Delaware so that there now exists a free press through which I can express an educated opinion of a scientific article in The Post. “Quack! Quack!” best expresses that opinion.

Oscar I. Dodek Jr., Bethesda

We’ve long had the “God of the gaps” concept, in which supernatural stories are used to fill in what science has not yet explained; for instance, thunder coming from the angered god Thor. Now, this article by a Catholic psychiatrist on exorcism introduces us to the “Devil of the gaps,” which accounts for weird behavior that psychiatry has not yet explained. My favorite part of the essay: The Devil speaks Latin!

Linda LaScola, Washington

The writer is co-founder of the Clergy Project.