The title is taken from Alexander Pope’s 1717 poem, Eloisa to Abelard :

Hurt and vengeful, Joel decides to undergo the same procedure. However, as the film descends into the "interior landscape" of his mind, Joel realizes mid-process that he doesn't want to lose the beautiful moments he shared with Clementine. The narrative becomes a surreal race through his crumbling memories as he tries to "hide" her in distant corners of his subconscious. Why the Title Matters

The film follows Joel Barish (Jim Carrey), a reserved man who discovers his ex-girlfriend, the impulsive Clementine Kruczynski (Kate Winslet), has undergone a futuristic medical procedure at a clinic called to erase all memories of their relationship.