When I wrote The Weir back in 1996, it was supposed to play for a few weeks at London's Royal Court. When people ask me why I think it's still running now I have to say I really don't know. Because people like ghost stories? Because it's not very long? (one hour, 45 minutes). No interval?

When I write something I never do it because I'm trying to make some point. But that so many people seem to have read so much into that particular play naturally makes me feel self-conscious about it. Ian Rickson, who directed it, says he thinks Irish playwrights prove so popular because our country is in a state of flux. There's an energy created by writers trying to figure out what's going on, and trying to voice it through characters. I have to say I don't know if that's true. But I always resist the notion that we are driven by anything unconscious.

I like to know what's going on. And, stupidly, I often pretend I do. I once heard an academic remark that the popularity of The Weir was due to its representation of Old Ireland meeting New Ireland. The men who drink in the bar are the remnants of Old Ireland.

They are comfortable with superstition. They are secure in their community and each knows his place in the pecking order. Then a woman from Dublin arrives and she is representative of the newer, changing, modern Ireland. Expected to fend for herself as an individual, she feels abandoned and has become dysfunctional. She's lonely and confused. The men in the bar take it upon themselves to console her. They accept her belief that she has had a terrifying supernatural encounter and they don't judge her.

And, just as all of us often feel like we'd like to take off somewhere for a while and sort ourselves out, this reading of the play suggests that New Ireland is a cold, alienating place where you are supposed to make decisions in a climate of uncertainty, and Old Ireland was a place where we'd like to go now. Even for a little while. Hear the old stories. Sit by the fire. Share your troubles.

I can see why, especially in urban environments like London and New York, people see the play as some kind of consolation. And perhaps more so with ex-patriates and people of Irish descent.

As I say, I don't know if this is why the play has been so popular. It's fairly plausible. But if this is the reason, my new play, Dublin Carol, won't have as easy a time.

Dublin Carol opens with an undertaker, John Plunkett, dispensing his views to his young assistant, Mark. John is in his late fifties. Mark is 20. The generation gap lends their conversation a slight awkwardness. Mark is shy but well-mannered and courteously listens to John's homespun advice.

Then John's daughter, Mary, arrives. She is about 30. She has some bad news about a relative of theirs. It turns out that John has not seen any of his family for many years. He seems to have been a fearful man who was convinced that the world was a bad place. Unable to bear the responsibility of protecting his family from imagined dangers, he simply abandoned them. He tries to explain this to Mary but she is bewildered by it.

Mary: No-one was going to attack us.

John: I know that! But this was a thing that I couldn't help feeling. And it was a terrible fucking feeling to have. And I just believed in it. And I sort of, let yous all down, just to get it over with. Or something. (Pause). I don't understand it.

Later on, Mark returns for his wages and chats again with John. He has had a terrible afternoon with his girlfriend. John's advice is that Mark should forget about her because he's be better off in the long run. Mark, who is a little drunk, reacts sharply.

Mark: That's bollocks.

John: What am I supposed to do? Stand here and defend myself all day?

Mark: Well then don't be dispensing fucking . . . wisdom . . . I feel like a fucking asshole! You're here telling me what to do? (Fiercely) I just feel like a fucking eejit!

John: I'm only trying to help you! Why don't you let me finish? I'm like the opposite of you . . . What? Am I talking to you like you're a kid? Is that it?

When they calm down it is John who turns to Mark for advice. About his family. And it appears that John is willing to take it and listen to the younger man.

Without giving too much away, not much else happens. (There isn't a huge plot in the traditional sense). But if we apply the "New Ireland relating to Old Ireland" reading to Dublin Carol, it seems to be saying the opposite to what The Weir is saying.

John seems to come from a place where he was constantly told he was fairly worthless as a person. Catholicism as an education stressed his need to be redeemed. Though perhaps he was never quite sure what he was doing wrong. And, while he may have been told that Jesus would forgive anything, it still meant that he had done something which needed to be forgiven.

Mark and Mary come from the newer, changing and changed Ireland. They've been exposed to different cultures and are capable of seeing more than perhaps just "both sides" of an argument. They come from an Ireland where when someone tells them they are bad people, they can simply answer "Why?"

Again, let me stress that I don't know if this is what Dublin Carol is necessarily "about". But if it's true that people see The Weir as a sort of Old Ireland - good, New Ireland - bad play and that this is why they've liked it, it's going to be interesting to see what the same audience will make of this one.

Dublin Carol opens at the Royal Court, London, early in the New Year