Beauty surfaces in various forms in the novel. Everyone marvels at Nastassya Filippovna's beauty. Aglaya is renowned for her beauty. The Yepanchin girls mention that beauty is power. Myshkin remarks that beauty is an enigma. During the engagement party at the Yepanchins the Prince exclaims that beauty can be found in all of God's creation. Pervading the novel is a sort of spiritual beauty to the character of Prince Myshkin and to the love he displays toward all the other characters. Indeed, such beauty is an enigma because it is a feeling and, therefore, impossible to define. Significantly, by the end of The Idiot, all the examples of beauty in the novel, including Nastassya Filippovna, Aglaya, and Myshkin, are ruined.
Dostoevsky strikes a contrast between light and dark from the outset, juxtaposing descriptions of Rogozhin's dark hair and eyes with Myshkin's light hair. Practically everything that involves Rogozhin is dark—his appearance, his house, the hall in which he tries to kill Myshkin, and the study in which he kills Nastassya Filippovna. Darkness is also frequently associated with Nastassya Filippovna: she wears a dark dress at the evening party, and thinking of her makes Myshkin think of darkness. Myshkin, on the other hand, writes the letter to Aglaya as to his "light." Aglaya's name itself also means "light." The contrast between light and dark emphasizes the contrast between the goodness of the prince and the corruption of the world around him. This contrast also underlines the different effects Nastassya Filippovna and Aglaya have on Myshkin: while the former fills his soul with darkness, the latter fills it with light.
Dostoevsky gives examples of many types of love: love out of vanity, passion, romantic love, and pity. Ganya's affection for Aglaya is vain love; he is not willing to sacrifice all for it, as we see in Part I when he asks Aglaya for some kind of insurance before he is willing to break off his engagement with Nastassya Filippovna. Rogozhin's feelings toward Nastassya Filippovna exemplify all-devouring passion; this kind of love approaches hate and is very destructive, both to the lover and the object of love. Both Nastassya Filippovna and Aglaya exemplify romantic love in their feelings toward Prince Myshkin, who in return loves Aglaya with romantic love. Finally, the strongest love of all in the novel is compassionate love, or pity, embodied in Myshkin and directed particularly strongly toward Nastassya Filippovna.