And, skipping over the details of all his supporting arguments, here's how he explains it.
Picture your memories as a stack of translucent papers with images on them. You can look at those papers in either of two ways.
- You can pick up one of the papers and let your eye wander over the picture on it, taking in all the details of that one image.
- Or, you can pick up a bunch of papers and hold them all up to the light together. If you did this, the unique details of each would blur away: only the most similar parts shared by most or all of the pictures would stand out.