The strongest argument against the existence of God, is that people say there is too much of evil in this world and too much suffering therefore there is no God. But can you not then see what is brought in through the back door in that question. Because if there's evil, there's good, if there's good there has to be a moral law, if there's a moral law there has to be a transcendent moral law giver but that's what the question is trying to disprove and not prove. Because if there is no moral law giver then there's no moral law, and if there's no moral law there's no good and if there's not good there's no evil, and then what is the question really?
So the strongest argument against the existence of God actually assumes God in the question.
-by Ravi Zacharias