From christiananswers.net ...
To say categorically, "There is no God," is to make an absolute statement. For the statement to be true, I must know for certain that there is no God in the entire universe. No human being has all knowledge. Therefore, none of us is able to truthfully make this assertion.
If you insist upon disbelief in God, what you must say is, "Having the limited knowledge I have at present, I believe that there is no God." Owing to a lack of knowledge on your part, you don't know if God exists. So, in the strict sense of the word, you cannot be an atheist. The only true qualifier for the title is the One who has absolute knowledge, and why on earth would God want to deny His own existence?
The professing atheist is what is commonly known as an “agnostic” - one who claims he “doesn't know” if God exists. It is interesting to note that the Latin equivalent for the Greek word is “ignoramus.” The Bible tells us that this ignorance is “willful” (Psalm 10:4). It's not that a person can't find God, but that he won't. It has been rightly said that the “atheist” can't find God for the same reason a thief can't find a policeman. He knows that if he admits that there is a God, he is admitting that he is ultimately responsible to Him. This is not a pleasant thought for some.
It is said that Mussolini (the Italian dictator), once stood on a pinnacle and cried, "God, if you are there, strike me dead!" When God didn't immediately bow to his dictates, Mussolini then concluded that there was no God. However, his prayer was answered some time later.