I just watched Memento. I know people have quoted the conversation between Leonard and Teddy/John Edward Gammell in full, but I have not seen the final inner monologue of Leonard discussed in detail. It may or may not contain answers to all the questions the movie raises, but to me it seems to summarize everything the rest of the movie has shown us about this character.
As Leonard is driving away from the scene where he has decided to set everything in motion to kill Teddy/John Edward Gammell (the ending of the story shown at the beginning of the movie), the following occurs:
We see Leonard looking ahead at the road as he thinks, "I have to believe in a world outside of my own mind." He then turns his gaze to his left hand and thinks, "I have to believe that my actions still have meaning, ..." The camera shifts to his point of view and we see on his left hand the tattoo of "remember Sammy Jenkis" as he thinks "even if I can't remember them." He then returns his gaze to the road and thinks "I have to believe that when my eyes are closed, ..." He closes his eyes and thinks "the world's still here."
We then start to flash back and forth between him with his eyes closed, and pictures in his mind of the sides of the road he is driving along and his wife laying her head on his chest (in color). At this point he thinks "Do I believe the world's still here?" His wife's hand on his chest moves to reveal the tattooed words "I'VE DONE IT" on his left breast under the mirrored words "RAPED AND MUR" while at the same time covering all visible parts of the "find him and kill him" tattoo written across his heart. She turns to look at his face as he thinks "Is it still out there?"
He then opens his eyes and thinks "Yeah. We all need mirrors to remind ourselves who we are. I'm no different." We then see him driving until he screeches to a halt in front of the Tattoo parlor. After stopping he pulls up a note in his left hand that he wasn't holding previously. He reads the note which says "TATTOO: FACT 6 CAR LICENSE SG13 7IU" and thinks "Now, where was I?" Fade to black.
Does the inner monologue at the end of the film Memento summarize the character? Is this monologue significant for understanding Leonard and if so how? There appears to be much more revealed here than just the "I'VE DONE IT" tattoo that everyone talks about.