themes and metaphors of"Doctor Zhivago"

Impossible love seems to be an overriding theme in this book. Check out this link

http://answers.yahoo.com/question/index?qid=20090226234955AA0tZL1

Keeping in mind that "impossible love" is a theme, I think the climax is when Yurii and Lara have to separate. Komarovsky tells them that they both have to leave Russia because they are in big trouble. Yuri deceives Lara and smuggles her out with Komarovsky (and Katya). So sad sniff sniff!