Brain researchers have found that if a certain part of a person’s brain is electrically stimulated, he may experience a strong feeling of the presence of God.
Therefore (some writers conclude), we don’t think God is present because God is really present, but merely because our brains our brains make us feel that He is.
This is like saying that since my brain can be manipulated to make me hallucinate an imaginary cat, there is no reason to think that I ever see a real cat.