In some ways it seems a bit of a puzzle that in A Portrait of the Artist as a Young Man, which was published a century ago, James Joyce's alter ego, Stephen Dedalus, listed silence as one of his three chosen weapons:

“I will tell you what I will do and what I will not do. I will not serve that in which I no longer believe, whether it calls itself my home, my fatherland, or my church: and I will try to express myself in some mode of life or art as freely as I can and as wholly as I can, using for my defense the only arms I allow myself to use – silence, exile, and cunning.”

Exile is obvious enough, and cunning (both low and high) is essential to art. But surely silence is the enemy of expression? Well, not in Irish writing it isn’t.

I was thinking of this in relation to two books I read recently. One is Sebastian Barry's wonderful Days Without End, which won the Costa novel award this week. It is beautifully expressed. But it is even more powerfully silent. Ludwig Wittgenstein famously warned that "Whereof one cannot speak, thereof one must be silent." And one of the motors of Irish writing is that there is so much that cannot be spoken of.

In this case, it is the Great Hunger. Barry’s Thomas McNulty is a refugee from the famine, a survivor of horrors. But what makes the novel so potent is that so little is said of all of this. We get just enough of it to understand Thomas’s capacity for cruelty as a solider in the Indian wars. The aesthetic force, though, lies in the withholding:

“Hunger takes away what you are. Everything we were was just nothing then. Talk, music, Sligo, stories, future, past, it was all turned to something very like the shit of animals . . . And that’s enough of that, I say, I don’t want to say no more. Silence.”

Less history

This centrality of silence is why it is not quite right to talk of Days Without End as a historical novel. True, it is a novel set in the past, and it involves itself with actual historical events, especially the genocide against the Indians and the US civil war. But the historical novel, rooted in the traditions of Walter Scott and Leo Tolstoy, aims to be as much history as it is fiction.

In Britain, for example, Hilary Mantel's novels delve very deeply into the major historical forces at work in the periods she sets them in (Tudor England in the case of the Thomas Cromwell novels) and seek to understand them as thoroughly and precisely as any historian using archival sources. But the Irish novel of history isn't really like this. It has too much silence in it. There are some proper historical novels in the Irish tradition – James Plunkett's Strumpet City being the outstanding one – but they are untypical.

I was thinking of silence, too, in relation to a completely different set of stories. I was looking again at the Icelandic sagas, those astonishing creations of the 13th century that foreshadow the European novel in so many intriguing ways. Silence arrives in one of them, and it arrives with an Irish character.

One of the big figures, Hoskuld, decides to buy a woman to serve as a sexual and domestic slave. The slave trader has a dozen women on offer, but Hoskuld is drawn to one who is raggedly dressed but good-looking. Before the deal is done, the trader warns Hoskuld that she has a major defect: “The woman cannot speak. I have tried in many ways to get her to speak, but never got so much as a word from her.”

After he brings her home, the young woman, who is both in exile and cunning, continues to use silence as one of her weapons. It is only after Hoskuld has fathered a child with her that he is out in the fields one day, hears voices and follows the sound. There is the slave woman speaking to her little son: “He realised she was anything but dumb, as she had plenty to say to the boy.” She has to admit that she can speak after all and to reveal her name and history.

Speaking Irish

“If you wish to know my name, it is Melkorka . . . My father is Myrkjartan [presumably MaCartan]; he is a king in Ireland. I was taken captive there at the age of fifteen.” Afterwards, we discover that the language Melkorka has been speaking is Irish. Her son Olaf grows up speaking it so fluently that when he sails to Ireland to find his grandfather, he is well able to communicate with the natives.

There’s a direct link between the Melkorka’s silence and Thomas McNulty’s. Their silences are strategic and they function as ways of dealing with, and surviving, traumatic exile. We have learned to think of silence only as a kind of illness – with very good reason; “breaking the silence” has been a major theme of recent Irish culture. But it has also been a weapon with which to fight oblivion.

Joyce knew that and chose not to write directly about so much of what he knew. Irish writers have long followed his example in tapping into the power of the unspoken – and the unspeakable.