How is the Theme of Fidelity Explored Throughout the Novel?

Fidelity is both a motif and a theme in Tolstoy’s Anna Karenina. The novel opens with a drama surrounding Oblonsky’s infidelities and features an affair as one of its chief story-lines as Anna Karenina and Count Vronsky fall in love and pursue a relationship outside of marriage. Fidelity (and infidelity) in the context of marriage is only one way the novel takes up this notional concept, however.
A great majority of Levin’s conflicts can be framed as a struggle to attain an internal fidelity. Being true to himself, as it were, is Levin’s central fixation. Exerting great efforts and suffering significant anxiety, Levin grapples with questions of how best to live in ways that are directly related to a fidelity of spirit, as it were, and a pursuit of self-knowledge. Thus fidelity is a thread that ties the novel together in terms of concerns with marriage and with individual integrity.