By Blaise Pascal
As he was working on Anna Karenina, Tolstoy underwent a spiritual crisis, like the one he shows Levin going through in the last part of the novel. Tolstoy describes how Levin had sought answers to existential questions in the works of the philosophers Plato, Spinoza, Kand, Schelling, Hegel and Schopenhauer (p. 787), but found no lasting satisfaction in their works. Where Tolstoy himself found religious comfort during this period is in the Thoughts of Blaise Pascal. After discovering Pascal in 1876 (or rediscovering him, because it's likely that he had read him earlier as well), Tolstoy enthusiastically recommended him to relatives, friends, and eventually his reading public. Quotations from Pascal appear in Tolstoy's later works.
When Pascal died in 1662, he left behind a collection of written fragments about the very matters that drove Tolstoy, along with his fictional hero, to despair. Pascal writes, in a searing way, about terror in the face of death, about humankind being like convicts awaiting execution, about fears that God has forsaken the universe and us along with it, about the individual's isolation as he or she faces death, as well as about frustration about the limits of language—words often seem inadequate to express what he feels in his soul. But in the midst of this despair, Pascal also writes about the necessity of faith, about the need to search actively for God. According to Pascal, the human lot is to feel an unbearable sense of emptiness, which can only be filled by God. All other human endeavors, whether worthwhile or destructive, are incapable of filling this void. Tolstoy shows Levin and perhaps Anna as well coming to the same conclusion.