In the structure of the Harry Potter books, the Chamber of Secrets and the Half-Blood Prince stand in direct parallel. They are, of course, both the middle book in a pair of trilogies. They both feature Aragog the spider. In both books Dumbledore is removed from Hogwarts, in Chamber by being striped of his Headmastership, and in Prince by his death (thus, in some way indicating that his removal in Chamber is a sort of death). In Chamber, Hagrid is exiled to Azkaban; in Prince, Hagrid is exiled from Hogwarts by the death eaters, who destroy his cottage.
There are many parallels we could meditate on, but the one I want to focus our energies on this time is the parallel and contrast between Gilderoy Lockhart and Horace Slughorn. I believe there is a case to be made that there is a structural parallel between the two men, but also a contrast. They both similar to one another, yet different enough that Slughorn is shown to be, in some ways, the restoration or undoing the wrong which Lockhart commits in Chamber.
Both Lockhart and Slughorn are both ambitious and oriented towards fame. Lockhart, of course, steals or if you will “collects” the memories of others for his own gain; Slughorn “collects” students who seem sure to flourish later in life for the benefits of knowing such rich and famous people.
Harry encounters both Lockhart and Slughorn only unwillingly, though both desire to take him under their wing (in this, there is also a likely parallel between both of them and Ludo Bagman as well). Lockhart is constantly trying to co-opt Harry for his own purposes, though Harry loathes him. Slughorn too wishes to “collect” Harry for his own purposes, and the only reason he is allowed to do so is because Dumbledore has asked Harry to “get to know” Slughorn.
Both Lockhart and Slughorn are parallel to one another in their meaning for Harry. They are, if you will, different contrasts to Harry. Lockhart is a Gryffindor, and Slughorn a Slytherin; Harry bears affinity to both, and Rowling has said that Harry has a fair bit of ambition in him as well as bravery. Thus, Lockhart and Slughorn are presented to Harry (and to us) as potential alternative versions of Harry, or who Harry could become.
Like Lockhart, Harry is a celebrity, but unlike Lockhart, Harry is also a hero and doesn’t really care for his celebrity status. Lockhart is the epitome of the “false Gryffindor,” the “cowardly lion,” if you will, spinning yarns about his bravado; this is, of course, the very real temptation of every Gryffindor – the very brave are also sorely tempted to boast of that bravery. Like Slughorn, Harry is very ambitious, but unlike Slughorn, Harry isn’t interested in ambition for its own sake. Where Slughorn wants a host of networked “friends,” Harry has no interest in befriending those he doesn’t like to get his way. He is happy with true friends; he is willing to lose friends and destroy his “network” for the sake of the truth.
But the connection between Lockhart and Slughorn is not entirely a parallel. The two men are also artfully contrasted with one another through their choices. Lockhart is the quintessential plagiarizer, stealing other people’s work for his own glory, whereas Slughorn has no particular desire to be in the spotlight himself, just the perks of knowing famous people.
Yet, it is in their choices in the final act of both Chamber and Prince that reveal the true contrast. Both Lockhart and Slughorn’s narratives climax around issues of memories – memories lost and memories gained. Lockhart, having revealed to Harry and Ron that he’s a fraud, intends to weave yet another story out of the situation, leaving Ginny to die and erasing the memories of Harry and Ron; in return, Ron’s damaged wand backfires on him and Lockhart’s own memory is taken. Lockhart’s final act, given the choice between celebrity and heroism, chooses fame and fortune, losing his own memories as a result.
Slughorn is then contrasted directly with this narrative of Lockhart’s. He conceals his memory of telling Tom Riddle about the Horcruxes for the purposes of his ambition – such a memory would harm his reputation. But confronted with the reality that his memory is the key in Harry’s mission to stop Voldemort – indeed, may even prove to tip the balances and show the way toward Voldemort’s final defeat – Slughorn chooses to set aside his private ambitions in service to the greater good, and he reveals the true memory to Harry. In so doing, he is a type of Lockhart, a parallel that ultimately subverts Lockhart’s own narrative. Slughorn is, in some ways, the restoration of Lockhart’s “fall.”