Maybe demons are defined as anything other than God that tries to tell us who we are. And maybe, just moments after Jesus' baptism, when the devil says to him, "If you are the Son of God…" he does so because he knows that Jesus is vulnerable to temptation precisely to the degree that he is insecure about his identity and mistrusts his relationship with God. So if God's first move is to give us our identity, then the devil's first move is to throw that identity into question.