I don't know about this...
"We" don't have any authority at all except that which is given by God above. He has all authority, there's no special power in us, I believe.
Like when I hear a reverend calling the church group to come forward and lay hands on the sick or raise their hands to heal someone...I'm like: What?! The healing isn't in our hands. We have no special healing powers. God is all of the power, God is all good.
When we stand face-to-face with a demon and declare that we have authority and the power to send the demon out, nothing's going to happen. Because we don't have authority, we don't have power. Our Father has the power, our Father has the glory. He can send that power through us...but it doesn't come from within us. Know what I'm getting at?
It's like that book, The Secret, where the author teaches that anything you want or desire, you have the ability to gain that something by using the special hidden powers from within yourself. You have the power to make your dreams concrete and possible.

*pfft!*
I don't believe that. We are powerless and weak. When we call on our Father, He channels the power through us, for His glory. If he sees that we believe and have faith in Him and that our needs are not selfish (I want to cast out this demon so that I can tell other people, maybe write a book on it and make some money to buy a schnazy car), He will grant us whatever we ask. Even the Holy Spirit, the presence of our Savior, the light, the Word, and evil runs from that. Evil doesn't run from us alone. Without God, we're nothing. Evil would laugh in our faces. Beckon us to join it. Tempt us.
It's not ours, but the Father's glory. All authority, all power, all understanding is His. We're His children, yes we are.

We can't take His authority and turn it into our own, for the purposes of granting our own wishes.
I don't know...that's what I thought of when I read that story. *shrugs*
