"I solmenly swear that I am up to no good."
These words open the infamous Marauder’s Map, an enchanted map of Hogwarts that shows the position of each and every person in the castle along with several secret passageways. The map, found by Fred and George Weasley, was made by a group of four boys who called themselves the Marauders. Ironically—but deliberately on Rowling’s part—the Marauders play a much bigger role in Harry’s life and in the narrative than one would think given the nature of the phrase. The map and the password to open it were intended for juvenile purposes—pranking, sneaking out of Hogwarts, and so on. Yet, in Harry’s hands, it will be used in life-or-death situations more than anything. This particular scene, in which the Weasley twins introduce Harry to the map, is also Rowling’s way of beginning to weave elements of Harry's past into his present. When we find out that Harry’s father and godfather, both, were part of the Marauders, the map is given much more weight in Harry’s life, and we see an early example of the novel's themes of time and consequences.
“Get off me,” Harry spat, throwing Pettigrew’s hands off him in disgust. “I’m not doing this for you. I’m doing it because—I don’t reckon my dad would’ve wanted them to become killers—just for you.”
Harry takes a moral stance in this scene, speaking to ideas of justice and who should be allowed to deal it out. Beyond that, he recognizes the moral boundaries held by his father—someone he idolizes despite never knowing—even when faced with a traitor like Pettigrew. Even though it would be easier and more satisfying in the moment for everyone involved (except for Pettigrew) to let Sirius and Remus kill him, Harry takes the higher, more difficult road and urges them to allow Pettigrew to be punished through the traditional, legal channels. Of course, this works out for exactly no one, but it was a solid effort on Harry’s part.
“Hasn’t your experience with the Time-Turner taught you anything, Harry? The consequences of our actions are always so complicated, so diverse, that predicting the future is a very difficult business indeed. . . .”
Time and consequences are prominent themes in Prisoner of Azkaban. Here, Dumbledore finally puts into words what Harry has learned through both his own actions and the actions of others. It is impossible to truly and easily predict what the future holds and what your actions mean for it (unless you’re Professor Trelawney, but she is often brushed off as a hack because of her eccentric personality despite always being right in some way or another). But, in this particular context, Harry believes Peter Pettigrew will bring back Voldemort, somehow, and that Harry’s mercy toward Pettigrew in the Shrieking Shack puts him at fault. But the relationship between cause and effect is much more complex than that, and even though Harry is right about what Pettigrew will do, he is wrong in his belief that it will be his direct fault if Voldemort rises again. Harry is but one player in the larger game that Voldemort has laid out and therefore cannot take the full blame for all the events that will occur later on in the series. Furthermore, he had no way of knowing that his act of morally conscious mercy would later allow Pettigrew to escape. Nothing is set, nothing is predictable, and our actions often have very different consequences than we would imagine.
"You think the dead we loved ever truly leave us? You think that we don't recall them more clearly than ever in times of great trouble? Your father is alive in you, Harry, and shows himself most plainly when you have need of him. How else could you produce that particular Patronus? Prongs rode again last night."
Dumbledore is speaking to Harry’s grief and confusion surrounding everything new he has learned about his parents and about their deaths. The ones we love may be physically gone from the world, but those left behind can hold them in their hearts, pulling strength from memories of them. Even though Harry never “met” his parents, he is a manifestation of their love, and living proof that love can transcend death. Harry is comforted by these thoughts, and holds onto this belief throughout the series, remembering and pulling some much-needed strength from it on his fated walk through the Forbidden Forest in Deathly Hallows.
"It all comes down to blood, as I was saying the other day. Bad blood will out. Now, I'm saying nothing against your family, Petunia ... but your sister was a bad egg. They turn up in the best families. Then she ran off with a wastrel and here's the result right in front of us."
Drawing on the prominent theme of "pedigree," a concern which in the Harry Potter universe is often associated with villains and death eaters, Marge suggests that Harry is a problem child because his parents were of "bad blood." The quote is especially relevant to Marge because she is a dog breeder, and the success of her trade relies on selective breeding, essentially eugenics. A consistent thread in Harry Potter is that the good wizards never buy into judgments based on a person's blood. For example, many Slytherins and prominent dark wizards loathe wizards who are Muggle-born and discourage "pure blood" wizards from having children with Muggles or Muggle-born wizards. In this way, Marge, a Muggle, aligns herself with the views of dark wizards.
"'The Grim, my dear, the Grim!' cried Professor Trelawney, who looked shocked that Harry hadn't understood. 'The giant, spectral dog that haunts churchyards! My dear boy, it is an omen—the worst omen—of death!'"
This moment confirms Harry's paranoid fear that there is a giant, black dog following him around. He recognized the black dog on the cover of a book about death omens in Flourish and Blotts, but now, in the setting of a Divination class, he is torn between his own understanding that there is precedent for Trelawney's prediction, and the skepticism felt by some of the smartest and most reliable people he knows, i.e. Hermione and Professor McGonagall.
"'I see,' said Lupin thoughtfully. 'Well, well ... I'm impressed.' He smiled slightly at the look of surprise on Harry's face. 'That suggests that what you fear most of all is—fear. Very wise, Harry.'"
This is Lupin's response when Harry tells him that the Boggart would have turned into a Dementor, had Lupin allowed him to face it himself. Lupin is impressed with Harry because the fact that Harry most fears a creature whose only purpose is to instill fear in people means that Harry's greatest fear is fear—which is almost like not fearing anything at all. The worst thing, for Harry, is to be afraid, because feeling fear prevents him from taking action and preventing bad things from happening.
"I gotta tell yeh, I thought you two'd value yer friend more'n broomsticks or rats."
In this scene, Hagrid makes Harry and Ron answer for their immature behavior towards Hermione, when they essentially excluded her from their group because she showed concern for Harry's wellbeing. Hermione's actions, especially with regard to Harry, always come from a desire to protect her friends. Harry and Ron are more focused on immediate gratification—flying a fast broom, going for a daytrip in Hogsmeade—but Hermione is focused on long-term consequences and big-picture problems.
"Never trust anything that can think for itself, if you can't see where it keeps its brain."
This is a quote Harry recalls after Fred and George leave him with the Marauder's Map while he weighs whether or not he should use it in this time of crisis. Arthur Weasley works for the Ministry and has encountered many dark artifacts, and he warns Harry against trusting objects that appear to have sentience and react and respond to stimuli in a seemingly logical way, because they have the potential to manipulate people. This is precisely what happened to Ginny Weasley in the previous book, The Chamber of Secrets, when she trusted a diary that wrote back to her. It was actually being manipulated by Lord Voldemort.
"I think the only reason I never lost my mind is that I knew I was innocent. That wasn't a happy thought, so the Dementors couldn't suck it out of me ... but it kept me sane and knowing who I am ... helped me keep my powers ... so when it all became ... too much ... I could transform in my cell ... become a dog."
In this quote, Sirius remembers how he kept his sanity in Azkaban, a place infamous for making even the most stable people go insane. When Hagrid, a fearless half-giant, recalls his time in Azkaban, he cowers like a normal human being. But Sirius clings to his innocence as a grounding technique. He says it is not a happy thought, because the fact that he is imprisoned as an innocent man is proof of grave injustice, however, the reality of the situation leaves him with the motivation to carry on. He had to keep his sanity if he ever wants to clear his name.