LEONARD
Memory's unreliable.

Teddy snorts.

    LEONARD
  No, really. Memory's not perfect. It's
  not even that good. Ask the police,
  eyewitness testimony is unreliable. The
  cops don't catch a killer by sitting
  around remembering stuff. They collect
  facts, make notes, draw conclusions.
  Facts, not memories: that's how you
  investigate. I know, it's what I used to
  do. Memory can change the shape of a room
  or the color of a car. It's an
  interpretation, not a record. Memories
  can be changed or distorted and they're
  irrelevant if you have the facts.