Faith vs. Denial

Romans 4

¹⁶ Therefore it is of faith that it might be according to grace, so that the promise might be sure to all the seed, not only to those who are of the law, but also to those who are of the faith of Abraham, who is the father of us all ¹⁷ (as it is written, “I have made you a father of many nations”) in the presence of Him whom he believed—God, who gives life to the dead and calls those things which do not exist as though they did; 

We have been given authority by God to do the same thing.  

(If you don't understand how or why you can read more here; http://www.speakfaith.com/articles/why_speak_your_faith.html.)

There is, however, a huge difference between

CALLING THOSE THINGS WHICH DO NOT EXIST AS THOUGH THEY DID

and

CALLING THOSE THINGS WHICH DO EXIST AS THOUGH THEY DO NOT.

The first one is faith.  The second is denial.