From Rita Skeeter’s exposés to the off-the-wall stories printed in The Quibbler, the magical community was as prone to a conspiracy theory and a gossip as much as us. In fact, some characters had theories on others that ended up being like our own, Muggle fan-theories.

Hagrid on Voldemort

Not only was Hagrid the one to introduce Harry to the wizarding world, he was also the first to mention Voldemort – and to voice this particular theory:

‘Some say he died. Codswallop, in my opinion. Dunno if he had enough human left in him to die.’
Harry Potter and the Philosopher’s Stone

With the discovery of Voldemort’s penchant for creating Horcruxes, it wouldn’t be long before Hagrid’s words were proved shockingly true.

Ollivander on wandlore

In many ways Garrick Ollivander’s theories about wandlore set the scene for Harry’s relationship with Voldemort. ‘The wand chooses the wizard,’ Ollivander told Harry, and who can say what might have been if the wand that chose Harry hadn’t been twin to Voldemort’s? Without that connection, Harry’s wand wouldn’t have absorbed the powers Voldemort unwittingly bestowed when he tried to kill Harry in the graveyard of Little Hangleton, and it wouldn’t have responded to Voldemort’s borrowed wand as it did during the Battle of the Seven Potters.

Ollivander’s theory of the wand choosing the wizard is important in another way. In their final battle, neither Harry or Voldemort used wands that originally chose them: Harry wielded Draco’s and Voldemort used the Elder Wand. But Voldemort was not the master of the Elder Wand and the fact that it recognised Harry as its true owner – based on his previous disarming of Draco – resulted in Voldemort’s destruction.

Harry on Draco being a Death Eater

Harry spent much of the sixth year nursing the idea that Draco Malfoy had become a Death Eater. His main piece of evidence was the way Draco threatened Burke with something unseen on his arm, something Harry maintained was the Dark Mark. This was not enough to persuade anyone else, although later events – plotting to kill Dumbledore, letting Death Eaters into Hogwarts – certainly proved Draco was up to no good.

All of which indicated what we now know to be true. Harry was right. Draco was a Death Eater.

Dumbledore on Horcruxes

Dumbledore always knew Voldemort would return – he said so when Snape approached him after the Potters’ deaths. Whether or not he suspected Horcruxes then isn’t clear, but he had certainly begun to consider them by Harry’s second year, with the appearance of Tom Riddle’s diary. It was at this point that Dumbledore also considered the possibility of multiple Horcruxes:

‘The careless way in which Voldemort regarded this Horcrux seemed most ominous to me. It suggested that he must have made – or been planning to make – more Horcruxes, so that the loss of his first would not be so detrimental…’
Harry Potter and the Half-Blood Prince

When Dumbledore learnt Voldemort had boasted of steps towards immortality, it solidified his thinking. When Harry secured Slughorn’s memory of Tom Riddle talking about seven Horcruxes, it confirmed it.

Hermione on the Chamber of Secrets

Hermione was one for theories. While she wasn’t always right – such as not believing the Deathly Hallows were real – her theory about the monster in the Chamber of Secrets moving through the castle’s pipes was life-saving. The fact that she delivered this information (technically) whilst Petrified made it even more remarkable.

Harry on Tonks and Sirius

Harry didn’t always get it right, either – he interpreted Tonks’s demeanour and changed Patronus as her having been in love with Sirius. That was wrong, as Tonks later revealed her love for Lupin. Harry wasn’t too far off the mark, though, unlike some…

Luna on Rufus Scrimgeour being a vampire

Luna certainly believed a lot of impossible things – including the fact that Rufus Scrimgeour, Minister for Magic during Voldemort’s rise, was a vampire. The fact that Scrimgeour was later killed by Death Eaters seemed to contradict this, but, well, you never know.

Harry on Dumbledore

He might have felt like Dumbledore had left him in the dark, but Harry did achieve some understanding of the man who helped shape his life. As Harry learnt about the Deathly Hallows, he formulated a theory about Dumbledore, the Elder Wand and that duel with Grindelwald. Yet the fact that Harry realised Dumbledore had the Elder Wand and still chose to focus on Horcruxes shows that, despite his doubts, Harry kept his faith in Dumbledore.

Dumbledore on Harry and Voldemort

Dumbledore always knew there was a possible connection between Harry and Voldemort.

‘I guessed, fifteen years ago,’ said Dumbledore, ‘when I saw the scar on your forehead, what it might mean. I guessed that it might be the sign of a connection forged between you and Voldemort.’
Harry Potter and the Order of the Phoenix

Dumbledore’s theory about that connection developed as Voldemort returned to strength. The revelation that Harry was a Parselmouth, the fact that Voldemort took Harry’s blood, Harry’s insight into Voldemort’s thoughts – the two were clearly deeply connected. Somewhere along the way, Dumbledore not only concluded that Harry was the Horcrux Voldemort never intended to make but that it would save him, in the end.

It was a bold theory. But Harry’s faith was rewarded, because Dumbledore was right. Of course.