To conclusively state that x does not exist, one would have to have absolute knowledge of the entire set. The larger and more inclusive the set becomes, the more difficult it is to say that x does not exist. When one comes to the set that includes all of existence, it would become necessary to possess infinite knowledge in order to state conclusively that x does not exist. One would have to be aware of the entire spectrum of space and time in order to be certain that x does not exist. This is, of course, a logical impossibility.
Absolute negatives collapse into unreasonableness.
The situation becomes more complicated in this case. A person who states conclusively that there is no God is claiming to have absolute knowledge of the entire spectrum of space and time which happens to be an attribute of God called omniscience . So, a person who states conclusively that there is no God is in essence claiming to be God. Thus, the only certainty to be found in this person's claim is that he or she is stating that he or she actually does not exist. The atheistic position thus collapses in self-defeat.