Other Christian writers find Rowling's treatment of magic less acceptable than Lewis's and Tolkien's. In his essay "Harry Potter vs. Gandalf," Steven D. Greydanus notes that in the works of Tolkien and Lewis, magic is confined to alien realms with their own laws, whereas Rowling's world coexists with our own; he thinks this is wrong: "Lewis goes to great lengths to make clear just how dangerous and wrong, how incompatible with Christianity, is any form of attempted magic in our world." John Andrew Murray similarly observes that Rowling's work portrays magic as a natural force to be manipulated, while Lewis and Tolkien portray magic as a gift bestowed by a higher power: "Despite superficial similarities, Rowling's and Lewis' worlds are as far apart as east is from west. Rowling's work invites children to a world where witchcraft is 'neutral' and where authority is determined solely by one's cleverness. Lewis invites readers to a world where God's authority is not only recognised, but celebrated — a world that resounds with His goodness and care."