Nobel prize winner Orhan Pamuk's first novel was The White Castle, a gripping tale of friendship and identity. The narrator is a young Italian scholar, travelling from Venice to Naples, when his ship is attacked by Ottoman galleys. He is taken prisoner. One morning he is invited to the pasha's mansion. To his horror, the man who walks in the door has his face. This man - who they call Hoja, or ''master'' - is his doppelganger.

While the Italian is terrified by this mirror of himself, Hoja seems untroubled. After the young scholar helps Hoja with fireworks shows for the Sovereign, the pasha gives Hoja the Italian as his slave. The Turkish master is a savant of sorts, gifted in intellect and well-versed in science and philosophy. He is greedy for the Italian's knowledge: mathematics, astronomy, engineering and chemistry.

In no time he's speaking, reading and writing Italian, and has mastered the young scholar's lessons. They become peers, working together on mechanical and cosmological discoveries. Soon, they are friends - of a sort. For Hoja, they are like a secret cabal; an intellectual illuminati.

But this scholarly brotherhood is soon complicated.

Hoja is obsessed with the identity of the Italian, and that of Europe as a whole. He wants to know what makes a man what he is, and how he can know this.

Angered by the Italian's conceit about Western self-knowledge, Hoja makes his doppelganger write his memories down. The young man writes pleasant recollections of childhood, but Hoja is not satisfied. He wants indiscretions and transgressions.

The Italian scribbles his sins, and his master beats him, admonishing him (sometimes in jest, sometimes in earnest). After the young scholar accuses the Turk of being a coward, Hoja writes down his own memories and vices. Stories about the deaths of friends and parents, childhood dreams, sibling rivalries, university dalliances - these fill up page after page. Writing to one another, or for their masters, the Italian and his Turk are soon more intimate than husband and wife.

Together, they note tiny minutiae of life: a dog soaked in rain, the shapes in drying laundry, and the nuances of conversation. Their experience is fused.

By the end of The White Castle, it is impossible to tell the two apart. The narrator speaks of ''Him'', but we don't know if this is his doppelganger, himself, or the men they used to be.

As an old man in his Turkish country estate, the narrator writes, ''I loved Him, I loved Him the way I loved that helpless, wretched ghost of my own self I saw in my dreams … I loved Him with the stupid revulsion and stupid joy of knowing myself.''

In a way that is enchanting and terrifying, Pamuk illuminates friendship and love.

This is often idealised. The French essayist Montaigne spoke of his friendship with Etienne de la Boetie as the most perfect, in which strangers became one soul in two bodies - ''the seam which has joined them,'' he wrote, ''is effaced and disappears.'' Why? ''Because it was he, because it was I,'' wrote Montaigne. No rationale was needed, for this rare love was a world of its own - no ''I'', no ''you'', just a mystical ''we''.

What The White Castle reveals is the violence and terror of this coalescence. The intensity of friendship is often too much - they seek diversions at court, or become childishly brutal. Hoja is aggressive and cruel, and the Italian is petty and manipulative.

Perhaps Montaigne's experience was rare in its ease and joy, or perhaps he was glossing over its ills. In either case, what Pamuk's tale suggests is that even the most tightly knitted friendships have friction and resistance. It takes extraordinary fervour to give one's consciousness over to another.

Having one's own mind probed and penetrated can be violating and exhausting. And then there are the duties, favours, promises and confessions. Genuine friendships, romantic or platonic, are hard work: worrying, baffling, tiring. And yet, the reward is precisely as Pamuk evokes, and Montaigne explains: the enrichment and expansion of our world, and a heightened awareness of life.

Cheers, my friends.

>> Dr Damon Young is a philosopher and author. His new book, Philosophy in the Garden, is published by Melbourne University Publishing.