The Reverse Genius Principle.
9) And that’s when we realize we could never be sure of anything to begin with.
8) When Leonard eventually thinks he has found his wife’s killer, eleventh-hour reveals shock us with the possibility that his whole crisis may be nothing more than delusion.
7) Editing MEMENTO must have been like navigating inside Las Vegas hotels with no watch or compass: sex and drug distractions, deprivation of day or night, no signposts or exit signs, and of course, nauseous on cheap shrimp and hairy tequila. Untold credit to editor, Dody Dorn, for shuffling the deck as confusingly as possible, yet weaving the tale as tightly as a sanitarium wicker basket.
6) But every few minutes, the movie twists back on itself, each flashback a segment of Leonard’s life that happened just before the segment we have just seen – and with each flashback, we realize just how wrong Leonard is about who his friends are, his past life, clues to the killer, his quest in toto. By about the fourth paragraph we realize: this piece is running backwards.
5) From Jonathan Nolan‘s short story, Memento Mori, we meet Leonard mid-investigation, slumming it in a cockroach motel, having lost his job as insurance consultant, looking disheveled (as Pearce can do so natchelly), and optimistically on the trail of the murderer; hanging with gregarious Teddy (Joe Pantoliano), and involved with hot bod, Natalie (Carrie-Anne Moss), both of whom seem to be aiding Leonard catch his killer.

…must remember not to forget…
4) Leonard’s last “new memory” was the murder of his wife. During the scuffle with his wife’s killer, a blow to the head caused his memory faculty to shut down. Whether this is truly biologically possible (if you cannot make new memories, how do you even shop for food and water or pay the rent?), for the movie’s purposes, it means Leonard must piece together clues to his wife’s killer through copious notes, tattoos on his own body and Polaroids. But the truth will forever elude him and the clues that lead to the killer are mere wraiths, the products of his own “selective” reasoning.3) The harder you strive for something, the harder it is to grasp. But what you care least about – or that you were never striving for – falls into your lap. Some call this the path of least resistance, but it’s actually called The Reverse Genius Principle. And Leonard – all ephemeral ideas and misplaced action – is a Reverse Genius in full throttle.
2) Guy Pearce is the memory-challenged Leonard, who is trying so hard to move forward – to find his wife’s killer, but unable to create “new memories” to retain info – that he ends up moving backward. Thusly, writer-director Christopher Nolan has crafted a film where the clues to a murder fall neatly OUT of place. Backwards.
1) MEMENTO opens with a killing. We don’t know why. We don’t know who.
END