What is the theme in The Unbearable Lightness of Being by Milan Kundera?

For all of its other concerns, The Unbearable Lightness of Being is first an exploration of the many facets of love. In his or her own way, each of the four main characters confronts and wrestles with the notion of love. Tomas, for example, never equates sex with love. Before Tereza comes into his life, he is very happy with his "erotic friendships." Because these affairs do not pretend to be "love" affairs, he is able to move among many women without betraying any of them. When Tereza arrives at his apartment and becomes ill, he realizes that he feels compassion for her, and that compassion itself is love. In spite of his many affairs, he does not leave Tereza, nor is there any doubt he loves her deeply.