Dostoevsky was almost successful in creating the "perfectly good man" in The idiot. Myshkin is indeed "perfectly good," but the question of whether or not he is truly a man is at the core of the book's tragedy. Myshkin's behavior and his attitudes are as close to being ideal as were those of knights-errant — or Christ; but knights (Don Quixote, for example) and Christ are figures incompatible with the real world of basic, animal self-interest and passion. Myshkin is another of those heroes from Western literature and from the Bible whom we are taught to admire, yet whom we learn — from experience — not to emulate too closely if we are to survive.
Myshkin is impulsively honest; we admire his honesty but we learn early when to be honest and how to be truthful; we learn the art of telling the truth and of being tactful. Also, we learn not to trust, as Myshkin trusts, proven liars and hypocrites. And, we also know, as Myshkin does not, to avoid neurotics and potential murderers. This practical code of behavior is our common-sense maturity; it appreciates ideal standards of behavior but it has another standard of behavior for day-to-day living. Ideal behavior belongs to the world that feeds our soul, like beautiful music and art, but it has little usefulness in practical living. Myshkin's view of reality is unlike any of the other characters in the novel. He returns good for evil; in Dostoevsky's own words, Myshkin "does not recognize that any sin is unforgivable." He is humble and meek and has no measure of pride, and, most important to a consideration of his character, he lacks sexual instinct. Akin to his lack of self-protectiveness and of drive, Myshkin has little of the animal nature that is present in other men. Thus, can one be a perfect man if he is sexless? Myshkin, although he is twenty-six years old, has no sexuality or lust, and though he abounds in compassion, he brings tragedy to Nastasya Filippovna, to Rogozhin, and to Aglaia because of his non-sexuality. With her background of well-subsidized eroticism, Nastasya cannot marry Myshkin and become his redeemed saint for the rest of her life; Rogozhin cannot conceive of Myshkin as not being a sexual rival for Nastasya, since Myshkin is male; and Aglaia cannot understand why, if Myshkin loves her, he broods over Nastasya Filippovna's acts of madness and why he finally decides to marry her. And, incredibly, Myshkin cannot understand the chaotic reactions of those three people to him.
One obviously cannot be a saint in today's highly sexual and materialistic world without something to brand one's goodness as different — as unnatural, as it were. Myshkin's excuse for his lack of sensuality and for his unworldliness is his epilepsy, but it fails to be a sufficient explanation for Rogozhin, Nastasya, and Aglaia, although historically epilepsy has been called "the sacred disease." To the other characters, Myshkin's epilepsy is merely an unfortunate, disfiguring, and embarrassing feature. Myshkin is strange, but he is handsome and therefore attractive to Nastasya and Aglaia — and a rival to Rogozhin and Ganya. The former admire him as women through the ages have admired handsome, gentle, and knight-like men; the latter distrust such exceptional, truly good types. In fact, a great many people distrust Myshkin's actions. All, from General Epanchin, at one end of the social scale, to his servants at the other end, themselves wear such thin masks of good-nature that they immediately assume Myshkin's character to be devious in proportion to its apparent sincerity and goodwill. They are wholly unprepared for the prince's genuine goodness; but they are quick to note his malleability.
Increasingly, as the novel progresses, the other characters manipulate the prince who has come from the snow-capped mountains of Switzerland to the bustling Petersburg, They manipulate him until he gradually learns to be wary of Lebedyev's lies and Ganya's schemes — until he finds that he is impotent to halt Nastasya's rashness and Rogozhin's murderous impulses. Finally, Myshkin's epilepsy returns as though to protect him from fully realizing the extent of greed and selfishness in his Petersburg milieu. His sickness returns to regrant him a vision of perfect harmony. When permanent insanity finally enfolds Myshkin, we realize that he will never again be frustrated by the chaos of the Ivolgins and the Epanchins, of Nastasya and Rogozhin. At last, as the prince so often yearned as the book neared its end, he is absolutely alone, utterly outside the idiocy of Petersburg.