To convince Tereza of his love for her, Tomas marries her and gives her a puppy. The dog is part Saint Bernard, part German shepherd, and Tomas suggests they name the puppy Tolstoy, after Tereza’s favorite book, Anna Karenina. The puppy is a girl, Tereza says, and she suggests they name her Anna Karenina, but Tomas doesn’t think the puppy looks like Anna. The dog looks more like Anna’s husband, Karenin, Tomas says, and after a short discussion on whether or not naming a female dog a masculine name will affect her sexuality, they decide to call her Karenin.
In the blending of both his breed (German shepherd and Saint Bernard) and his gender, Karenin collapses sets of opposites, making them meaningless and insignificant. This is a repeated theme throughout the book, and it points to another way in which language is unstable. While Karenin is biologically female, he is referred to with male pronouns throughout the book.
Even with Karenin’s help, Tomas isn’t able to make Tereza happy, and Tomas becomes acutely aware of this fact on the 10th day of Russia’s occupation of Czechoslovakia after the Prague Spring in August of 1968. A friend in Switzerland keeps calling to offer Tomas a job at a hospital in Zurich. Tomas’s friend is worried about Tomas in Czechoslovakia and wants him to immigrate to Zurich.
The power struggles of the Russian occupation are mirrored in Tomas and Tereza’s relationship. Just as Czechoslovakia has lost power to the Soviet Union, Tomas is losing power over Tereza, as he can’t seem to make her happy. Kundera later claims that a human cannot give another human the gift of happiness, but a dog can, which Karenin later does for Tereza.