Voldemort did not know that Harry Potter was a horcrux, as he unknowingly made him one when he was attempting to kill him as a baby.
In Harry Potter and The Half-Blood Prince, the mystery of Voldemort’s immortally is finally revealed when the matter of the Horcruxes is revealed.
A Horcrux is an object which contains a fragment of someone’s soul, so that if the person dies, a piece of their soul remains alive in the object.
It was initially believed that Voldemort had created six Horcruxes. A feat which was never achieved successfully by any wizard or witch in the past. However, the frequency thereof made his soul volatile, so when he tried to kill Harry, he unknowingly made his sixth Horcrux.
How many Horcruxes did Voldemort make?
Essentially, Voldemort knowingly made six Horcruxes, which included the diary, ring, the locket, the cup, the diadem and Nagini.
Nagini was Voldemort’ snake and the most ambitious Horcrux he made. This is as Horcruxes are usually inanimate objects, which makes them easier to hide.
However, the use of living animals or people was unheard of. Similar to the ability of creating six Horcruxes, which before Voldemort, no one had been able to successfully do so.
Harry Potter is the sixth horcrux he created, although, he is considered a pseudo-Horcrux as Voldemort was unaware of its creation.
Did Voldemort know Harry was a Horcrux?
Voldemort did not know that Harry Potter was a Horcrux. Moreover, Harry is considered a pseudo-Horcrux. This is because Voldemort did not intentionally make Harry one, as it happened when he attempted to kill Harry as a baby.
Essentially, Voldemort had intended to make a total of six Horcruxes, not including the two he unintentionally made. By the time he unknowingly attached his soul to Harry, he had made five of them.
The last, being Nagini, who was made after Harry Potter’s parents died trying to save him as Dumbledore explains in The Half-Blood Prince, “He seems to have reserved the process of making Horcruxes for particularly significant deaths.”
Going onto add, “I am sure that he was intending to make his final Horcrux with your death. As we know, he failed. After an interval of some years, however, he used Nagini to kill an old Muggle man, and it might then have occurred to him to turn her into his last Horcrux. “
How did Voldemort make Harry a Horcrux?
Dumbledore, best explains how Harry came to be Voldemort’s seventh, technically sixth, Horcrux in The Half-Blood Prince, by stating:
“You were the seventh Horcrux, Harry, the Horcrux he never meant to make. He had rendered his soul so unstable that it broke apart when he committed those acts of unspeakable evil, the murder of your parents, the attempted killing of a child. But what escaped from that room was even less than he knew. He left more than his body behind. He left part of himself latched to you, the would-be victim who had survived.”
How do you create a Horcrux?
Creating a Horcrux is a three-step, gruelling and excruciating process, hence no one was known to have successfully made more than one Horcrux. The first step involves committing murder in order to split the soul.
Thereafter, a spell is cast in order to separate the piece of the soul which will be placed in the object.
Lastly, you need to create mystery over the chosen object. Considering the process and the pain of it all, the question has always been how was Voldemort unaware that Harry was one of his Horcruxes? The simple answer being desensitisation.
Why did Voldemort not know that Harry was a Horcrux?
Voldemort did not know that Harry Potter was one of the seven Horcruxes he made, because he did not intend to do so.
However, after fragmenting his soul five times before already, it is believed that he was desensitised. Moreover, being a child that was conceived from a love potion, it is believed that that also impacted his sensitisation.
Therefore, by the time that his attempt to kill Harry backfired, his soul was so unstable and without feeling, that he did not feel it happen.
Conclusion
Harry Potter is saved from Voldemort’s fatal attack during the final instalment of the franchise, Deathly Hallows, from the love of his passed loved ones from the surface.
However, it is suggested that another reason he survived is that the fatal curse only killed the Horcrux and saved his life.
Voldemort did know that Harry Potter was a Horcrux at the time, as his only intention was to ensure that the prophecy which had set everything in motion did not come true.
A prophecy which had suggested that Voldemort needed to kill a boy more powerful than him or he would die.