It is very interesting to go through the different arguments for or against the existence of God in the Web.
One of the major problems is the very definition of God. Though there are different definitions of God it does not prove God's non-existence. On the contrary, it provides more reasons to believe God exists but God's very nature goes beyond human comprehension. In this case, REVELATION, God's self-manifestation, is of great or indispensable role.
In the Judaeo-Christian-Islam tradition, God's first positive Self-manifestation (in contrast to natural self-manifestation) can be traced to the Abrahamic experience. In Abraham's experience, God is a personal God and is actively involved in the lives of the believer.
The more positive Self-manifestation of God in the Old Testament is the Moses' "Burning Bush" experience. God identified Godself with existence: "I AM WHO AM".
Let me begin my Theological and Philosophical presentation of the nature of God here. God manifested God as existence. The very being of God is existence. Therefore, God cannot be non-existence.
God is in everything that exists as its creator, thus, everything shares in the very nature of God as created to be "good", and especially persons- created in God's "image and likeness."
Since God is in everything, everything is in God - under God's influence. What human beings discover about human-self, the cosmos (nature) are but God’s revelation of God’s very being.
Atheists can only deny God or a particular concept of God but they cannot annihilate God for it means annihilating existence Itself.