William Peter Blatty, author of “The Exorcist,” stands on the iconic steps from the movie. His latest, “Finding Peter,” asserts that his late son has been contacting him from beyond the grave. (Jim Lo Scalzo/European Pressphoto Agency)

Exorcist” author William Peter Blatty has a new book out. Titled “Finding Peter,” it’s part comic memoir, part argument for life after death. Blatty, a lifelong Catholic, lays out a number of curious incidents — electric lights mysteriously flickering on and off, etc. — that have convinced him that his son Peter, who died of a rare heart disorder in 2006 at the age of 19, has been communicating with him from beyond the grave.

Blatty, who calls his book a “labor of love” meant for readers who have lost a loved one, plans to donate the book’s royalties to a scholarship fund in his son’s name at Peter’s old high school, the Heights School, in Potomac, Md . We chatted with the 87-year-old Bethesda, Md. author by phone, touching on the literary life, life after death and movies.

Your book’s subtitle is “A True Story of the Hand of Providence and Evidence of Life After Death.” It’s telling that you use the word evidence — what a lawyer might present to a jury. That’s not the same thing as proof.

No, it’s not proof at all. Any one of even the most dramatic incidents that I cite in the book could be explained as coincidence. It’s only when they’re considered in the context of eight years of this kind of going-on that, for me at least, they take on considerably more weight.

The first half of the book establishes the credibility of the witness, as it were.

That is precisely what it does. There’s no film extant of me prowling around Stonehenge in the middle of the night wearing a white cloak and carrying a candle, singing “Moonlight Becomes You.” All of that prologue — all of which, by the way, is totally true — was to get the reader to know, and hopefully to trust, the witness.

Do you entertain the possibility of reincarnation?

Personally, I do. In the very early Catholic Church there were sects who definitely believed in the transmigration of souls. I’ve read a great deal about it. And maybe there’s something in my own life that tends to convince me it’s a possibility.

Who might that be?

Oh, God, then I have to name names. There is one person in my greater family who I’m convinced probably — let’s make that very probably — is a case of reincarnation.

You write that Peter’s death was as devastating as your mother’s death in 1967.

I grieved almost five full years, so deeply that some around me thought it was a morbid grief, over the passing of my mother. And yet, with one possible exception, I have never, to this day, received any kind of a sign or message from her like those I recount in the book concerning Peter.

Why do you think that is?

The flat-out honest answer is I don’t know, but I can make a fairly good guess. I’m sure you’ve heard of a film called “The Orphanage.” There is the character of a psychic, and she utters the following line of dialogue: “First you must believe, then you will see.” Maybe there were signs from my mom, but I wasn’t looking for them.

How has your faith changed since then?

At the time of my mother’s passing, my faith was probably more of a deeply intense hope. I was more of a relaxed Catholic.

The first part of the book is funny.

Well, I used to be a comedy writer.

Are you reminding readers of your pre-“Exorcist” past?

I don’t mean to remind them. Most of them probably never knew about it. Would you believe that, a million years ago, Martin Levin in the New York Times said, “Nobody can write funnier lines than William Peter Blatty?”

Has anyone who heard the Peter stories called you a kook?

No. First of all, I didn’t tell anything of this to strangers or shallow friends, only to a very few people who I trusted and who trusted me. I shared the stories with them, and two or three of them said, “You’ve got to do a book.”

Do you follow contemporary horror?

God, no. I’m not a fan. I tried to direct one [“The Exorcist III”] a long, long time ago. I’m not a fan of them since I saw a film called “The Manitou,” which was an American Indian version of “The Exorcist.” That’s enough to kill your appetite for the genre. I remember seeing “The Exorcist II.” I was the first one to giggle, and on my second giggle I got a sternly reproving look from the man sitting ahead of me. But I promise you that when Louise Fletcher put this helmet on top of Linda Blair’s head, the whole audience went up with me.

“The Exorcist” put forward the notion of evil incarnate.

I have moved away from the belief in fallen angels to the belief that demons are, in fact, spirits of the dead who are behaving very, very badly. In fact, in all of the possession literature since the beginning of the 20th century, most cases involve the spirit of someone who has died.

What message do you believe Peter is sending you from that realm?

I’m alive. I have not been extinguished. I have not plunged into oblivion. I care, and I am in communion. Of course, my Catholic faith believes in the communion of saints.

What’s next for you?

This is it. I am very happy with “Finding Peter.” Saint Paul tells us to do good while we can. At age 87, I am rushing like crazy to do a lot of makeup.