One feature of Dostoevsky's writing is the almost clinically objective style with which he details the unfolding events. The phrase "It is a fact that..." crops up quite often throughout the narrative. The account that Dostoevsky provides is resolutely factual, avoiding all traces of melodrama. This understated approach allows Dostoevsky to tell his story in a way that gives readers the best of both worlds—factual accuracy and artistic truth.

From this approach emerges the theme of appearance versus reality. It is instructive in this regard that the first three chapters are entitled "First Impressions 1, 2, and 3." Initially, readers enter into a world of appearances, which describes how things seem to the narrator. Yet in the surreal, nightmarish world of the prison colony, nothing is ever quite what it seems, as the reader subsequently discovers:

Reality is infinitely various when compared to the deductions of abstract thought, even the most cunning, and it will not tolerate rigid, hard-and-fast distinctions. Reality strives for diversification.

Prison life has its own rules, conventions, and strange rhythms. At once a  microcosm of the social world outside and a world entirely of its own, prison life is an amalgam of confusions:

Even though I looked at everything with keen and avid attention, I could not discern much of what lay under my very nose.

The narrator is applying the standards of the "radiant free world" to prison, yet it serves only to mystify rather than clarify. The narrator never truly understands prison life and all its unusual customs. However, he at least gains a deeper comprehension of the dark and degrading environment into which he's been thrust.

 The fact that the narrator never truly becomes—psychologically, at least—a hardened criminal leaves untouched the innate sense of freedom that nests deep within his soul. Dostoevsky's idea of freedom is presented here as relating to the inner freedom of the personality and soul, which can be compromised but never destroyed by incarceration. The narrator occupies a different social class from the other prisoners; this sets him apart. Although it makes daily life complicated, it nonetheless allows him to preserve his inner freedom and the integrity of his soul from the encroachments of the value system of the criminal classes.

At the same time, the narrator develops a sense of unity with the other inmates, a feeling that, for all their faults, they are still God's children. The narrator doesn't judge and doesn't want readers to, either. Instead, he allows the convicts to tell their own stories and indicates that they are still human beings with free will and agency. 

Despite their faults and misdeeds, the narrator suggests that one might learn from the innate folk wisdom possessed by the common people:

One has only to remove the outer, superficial husk and look at the kernel within attentively and without prejudice, and one will see in the common people things one had no inkling of. There is not much that our men of learning can teach the common people. I would even say the reverse: it is they who should take a few lessons from the common people.

Learning from the people, the Russian peasantry who formed the vast majority of the population, was a common political theme at the time when Dostoevsky wrote his story. It says something about the social hierarchy of Tsarist Russia that one of the few ways that members of the intelligentsia can truly empathize with the common people is by sharing their experiences of prison. Nevertheless, by doing so, they throw off the artificial constraints imposed upon them in the so-called free world and become reacquainted with their humanity.

It is in this sense that the narrator's experience of prison is educational, with his fellow inmates as teachers. On his final day in prison, when his shackles are finally removed, the narrator is not just a free man; he was reborn and resurrected as a human being. Humanity, despite all the myriad challenges and terrors of prison life, has ultimately won. And that, more than any other, is the most abiding theme of The House of the Dead.