Rowling has said that creating the story about Harry Potter 's past was a matter of reverse planning : `` The basic idea ( is that ) Harry â did n't know he was a wizard â and so then I kind of worked backwards from that position to find out how that could be , that he would n't know what he wasâ When he was one-year-old , the most evil wizard in hundreds of years attempted to kill him . According to Rowling , fleshing out this back story was a matter of reverse planning : `` The basic idea ( is that ) Harry ... did n't know he was a wizard ... and so then I kind of worked backwards from that position to find out how that could be , that he would n't know what he was ... That 's ... When he was one year old , the most evil wizard for hundreds and hundreds of years attempted to kill him .