There’s a lot about memory in Chamber of Secrets, especially these last few chapters. First of all, there’s Tom Riddle, who claims to be a memory rather than a ghost. Readers who have finished the whole series will know he’s something far more sinister than a memory of the type put into a pensieve, and yet, his diary works very much the same way for Harry when he shows him evidence of Hagrid’s supposed guilt. Just like in a pensieve, Harry is there without truly being there, unable to interact with anyone he encounters. It would seem that, along with a part of his soul, the diary does indeed contain Tom Riddle’s memories.
There’s also Ginny, who finds awful gaps in her memory that coincide with the times the attacks take place. Whenever Tom possesses her and forces her to set the basilisk loose on people, he does so without her knowledge and erases the events from her mind. This inability to remember is one of her very first clues that something is wrong.
Finally, Professor Lockhart’s one real talent turns out to be his memory charms. He has made a career out of tracking down witches and wizards who have done something heroic, wiping their memories, and taking credit for their accomplishments. In what can only be described as karma, one of his memory charms backfires, and he loses his own memories.
The importance of memory certainly doesn’t stop with Chamber of Secrets. It becomes a more and more important theme as the series progresses. In the next book, Prisoner of Azkaban, the story of Harry’s parents begins to take shape; in Goblet of Fire, Harry witnesses important events from the past through a pensieve; in Half-Blood Prince, he and Dumbledore explore many people’s memories in order to learn about Tom Riddle’s transformation into Voldemort and discover a way to stop him; and finally, in Deathly Hallows, it’s through memories in a pensieve that Harry finally learns what his Chosen One status means and that he will have to sacrifice his life to defeat Voldemort.
Even the spin-off stories place an important focus on memory. Albus and Scorpius from Cursed Child travel back in time to their parents’ school days and, eventually, the day Harry’s parents were murdered. The past is more important than the present to their story. Jacob Kowalski, from Fantastic Beasts and Where to Find Them, is a muggle who finds himself brought along on a magical adventure and falls in love with a witch, but loses his memories at the end of the movie. Amata, from “The Fountain of Fair Fortune”, cannot move on and be happy again until she lets go of her memories of the lover who abandoned her. She does this literally by removing them from her mind as a silvery liquid and throwing them into the river. And, of course, the whole point of Quidditch Through the Ages is to show the long history of the magical sport.
There are many important themes in the Harry Potter series, but memory is certainly one of them. Things that happened in the past – whether as long ago as the Hogwarts founders’ time or as recently as earlier in the series’ present-day timeline – keep on turning up and being important. The Harry Potter stories don’t often use traditional flashbacks, instead using things like the penseive and Tom Riddle’s diary to keep the reader in our present-day protagonist’s viewpoint but allow us – and Harry – to discover the past through magically-preserved memories.