Thick woollen socks. That’s what Dumbledore tells Harry he sees in the Mirror of Erised during their first ever face-to-face conversation in Philosopher’s Stone.

As an introduction to Dumbledore it’s pretty telling: an evasive answer, yes, but one given kindly and with his classic, whimsical sense of humour that stops Harry asking any more questions. Still, it’s a long time before we discover what the Mirror really reveals about Dumbledore’s deepest desires, given how careful he is never to reveal too much to Harry.

This is a pattern established early on, with Dumbledore taking charge of Harry’s future in the immediate aftermath of his parents' death. Professor McGonagall is horrified to think of Harry being brought up by the Dursleys, but Dumbledore is adamant that leaving him to the care of his Muggle relatives is for the best. Later, with Harry established at Hogwarts and Voldemort beginning his journey back to power, we hear repeatedly that Dumbledore is the only wizard Voldemort is afraid of, and yet he is absent when Harry comes face-to-face with the half-formed Dark Lord hiding under Professor Quirrell’s turban.

Which is all part of the grand plan, as we learn much later, but even after knowing Dumbledore for less than a year Harry begins to wonder about his enigmatic headmaster.

‘I reckon he had a pretty good idea we were going to try, and instead of stopping us, he just taught us enough to help. I don’t think it’s an accident he let me find out how the Mirror worked.’

Harry Potter and the Philosopher’s Stone

It might not be an accident, but it is a pretty unconventional approach to teaching. He also makes sure Harry has his father’s Invisibility Cloak but it’s a gift given anonymously, which again prevents Harry from asking any questions until Dumbledore is prepared to answer them. Or half-answer them, anyway.

All of which is to say that Dumbledore is a pretty mysterious man. But his penchant for keeping certain things to himself can’t hide his warmth and kindness: this is a wizard who trusts Hagrid with his life, gently reminds Harry not to dwell on dreams and notices and rewards Neville Longbottom for standing up to his friends. It’s a warmth that makes people trust him without question – Professor McGonagall does see the wisdom in his decision to leave Harry with the Dursleys, and everyone from Hagrid to Percy Weasley sings Dumbledore’s praises.

But of all the characters we meet in Philosopher’s Stone it’s hard not to look at Dumbledore, in particular, without factoring in everything we later learn. In Order of the Phoenix – five years after the events in Philosopher’s Stone, and only after the death of Sirius – he reveals his reasons for leaving Harry with the Dursleys and explains his motivation for not telling Harry the truth about why Voldemort had tried to kill him as a baby. Would knowing these things earlier have given Harry a better sense of how Voldemort might try to entrap him? Might it even have stopped him rushing to the Department of Mysteries, and so prevented Sirius’s death? Who knows, but it’s in Order of the Phoenix that Dumbledore starts to acknowledge to Harry that he may have made some mistakes.

And yet when he reveals the reasons behind his decisions, it seems that it was all pretty obvious from the outset. He cares about Harry. His primary objective is to keep Harry safe and as happy as possible.

Dumbledore’s thoughts on the Mirror of Erised make this pretty clear. Again, what we later learn about Dumbledore’s past can change what we think of his conversation with Harry – when he says the Mirror provides neither truth nor knowledge, is he talking about his own experiences? Is the gentleness with which he tells Harry not to come looking for the Mirror driven by the fact that he, too, knows what it’s like to dream of seeing your family again, whole and unharmed?

But these aren’t questions we thought to wonder about in Philosopher’s Stone – and nor, it seems, did Harry. It’s testament to Dumbledore’s character that none of us really doubted the wisdom of his choices, even without the full explanations that came later.

Yet there are moments in Philosopher’s Stone that hint at the darker days to come. Dumbledore’s words to Harry about the Mirror are not to dwell on dreams and forget to live. Again he could be speaking of his own history – his obsession with the Deathly Hallows, perhaps, and his neglect of his family – but he is also advising Harry, who will become so entwined with Voldemort’s brain that he starts to dream his dreams, something Dumbledore tries to get him to resist when he instructs Snape to teach Harry Occlumency in Order of the Phoenix.

As it later becomes clear, Dumbledore already knows what Harry must do to defeat Voldemort. In Philosopher’s Stone, he chooses not to burden Harry with that knowledge, telling him only that he will know more when he’s older. And in doing so, he – perhaps unknowingly – binds Harry to him in a way that will become increasingly important.