One of the best arguments for atheism I've found is at http://www.ebonmusings.org/atheism/burningbush.html
. I invite theists to try to refute ebon's argument.
Forgive the long post, I summarized it as much as I could by deleting some sections (. . .) and with small additions (in brackets [ ]).
One More Burning Bush: The argument from divine hiddenness
The argument so far can be summarized as this: When we study history, we encounter stories of great miracles and appearances of God. These stories are not corroborated by any similar events in the present. There are no reliable means for humans to detect the existence of God, and although theists tell us God has the power to bridge this evidentiary gap from the other side, there are no occurrences that can reasonably be interpreted as this happening. In short, God is absent, and evidence of his activity is nowhere to be found.
[T]he argument from divine hiddenness . . . builds on the fact that God's presence is not obvious, supplementing it with the proposition that, if God existed, there would be good reasons for him to make his presence obvious - and from there concludes that the most likely explanation for the lack of divine manifestations is that there is no divine being at all.
The lack of obvious manifestations of God is better explained by assuming that God does not exist than by assuming that God does exist but chooses to remain hidden.
[Formal Outline of the argument]
Assumption (1): God exists.
Assumption (1a): God desires that people be aware of his existence.
Assumption (1b): God desires that people worship him in specific ways.
Assumption (1c): God has the ability to make his presence obvious and explain clearly what he desires.
Premise (2): God's presence is not obvious in the world.
Premise (3): Many people do not believe in God because of a lack of evidence.
Premise (4): Many people who do believe in God do not agree on what he desires, because of a lack of evidence.
Premise (5): For God to make his premise obvious and explain his desires would remedy both (3) and (4), without having any significant negative side effects.
Conclusion (6): If God exists, he would make his premise obvious in the world and explain what he desires. (from (1),(5))
Contradiction: But no such thing has happened. (from (2))
Conclusion (7): God does not exist. (from (6),(2))
[T]here are some theistic traditions that face no difficulty from the argument from divine hiddenness. However, most religious traditions believe that God wants us to both believe in his existence and worship him in specifically defined ways, and it is these against which the argument from divine hiddenness is most effective. For if there exists a God who desires that humanity believe in him and come to know him, why would he not take the most effective possible action to ensure that this occurs?
Granted, this argument does not claim to offer certainty, only probability. The more confidence we have in its premises, the more confidence we can place in its conclusion; but these premises, like all our knowledge, cannot be absolutely proven.
God's existence is obvious. Those who deny this do so out of stubbornness or selfish personal reasons.
Even the most fervent of believers must admit that God's presence in the world is not obvious in the way it could conceivably be. If there is a deity, it could make its presence apparent in a way that requires no "inference" whatsoever. Why would God, if such a being exists, not reveal himself in a way that demonstrates intentionality and miraculous power and allows for actual communication? It is one thing to claim that the existence of pattern and regularity in the world implies a hidden intelligence behind it all; it is quite another for that intelligence to actually speak to us directly. While the former claim is uncertain and disputable at best, surely not even the staunchest atheist could deny a god that simply shows up and talks to us in the way that any close friend would. This defense to the argument from divine hiddenness cannot explain why God would not choose to do this, and therefore it cannot be considered a success.
For God to clearly reveal himself would violate our free will because humans would then have no choice but to love and follow him.
The most obvious counter to this argument is to point out that the traditions of most religions refute it themselves. For example, . . . [t]he Old Testament scriptures likewise tell of the Egyptian Pharaoh who refused to release the Israelites from their captivity despite overwhelming displays of God's power; the Israelites themselves repeatedly stumbled into idolatry throughout their history despite painful familiarity with the divine wrath that inevitably followed. . . . The list goes on and on. If it would be coercion for God to manifest himself, display miraculous power and demand our worship, as some theists hold, why is it that, according to those theists' sacred books, he did exactly that on many occasions in the past? Why was God not concerned about coercion then? And why is it not coercion when God's followers wrote down accounts of those miracles and presented them to others as truth?
Mere knowledge that he exists would not compel us to obey him, any more than we are forced to obey anyone else whose existence we are certain about. Even if we knew for certain that God existed, we would still be perfectly free to disregard his commands or reject him as a tyrant unworthy of our worship.
God does not clearly reveal himself because he knows that doing so would do no good; those who disbelieve and rebel would continue to disbelieve and rebel.
I am an atheist, as many others are, precisely because of the lack of credible evidence for the existence of any supernatural being. If this evidence was provided, I would believe, as would many others; imaginary personal motives have nothing to do with it. . . . If God exists and wants me to believe in him, there is no reason why he should not provide it. . . . To say that an unmistakable direct manifestation of God would not convince anyone to change their mind is to show a complete ignorance of human psychology. History teems with reports of vast numbers of seemingly otherwise rational people who willingly abandoned their families, their possessions and sometimes their lives to follow self-proclaimed religious leaders on the flimsiest of evidence. If anything, we as a species are too eager to follow authority.
God does not clearly reveal himself because he desires worship rather than mere acknowledgment of his existence.
True, belief in God's existence is not a sufficient condition for producing such a relationship, but it is certainly a necessary one. A person cannot love or worship what they do not believe to exist. Even granting for the sake of argument that an obvious manifestation of God would not produce mass worship (although in actuality it almost certainly would), it would lay the essential foundation on which such a response could be developed. Once a manifestation of the divine had made untenable the proposition that God does not exist, proselytizers could cease their efforts to overcome this objection and instead concentrate on providing reasons why God should be worshipped and obeyed. Surely this would be a much easier task!
God does not clearly reveal himself because worship based on miracles rather than faith would not be lasting.
However, any proposed solution to the problem of divine hiddenness must accommodate not just the fact that miracles do not occur today, but also the fact that they were once claimed to be abundant . [i]f God's performing miracles would only invite subsequent generations to demand to see more just as good as the ones their forefathers witnessed, then it seems he has already given the game away: the Bible and other holy books contain many accounts of dramatic, earth-shaking miracles. If not fostering people's dependence on him is God's paramount concern, then why did he perform them so often in the past?
God could reveal himself to us and interact with us in the same way human beings interact with each other - not in blazing displays of cosmic power, but in the simple, everyday ways that convey the message that the other party is there, that they are who they say they are, and that they are willing to communicate. These things are the basic and essential components of a relationship. Does it ruin your relationship with your best friend for you to be able to see them and talk to them every day? If not, then what justification can there be for applying a different standard to God?
Conclusion / One More Burning Bush
If God is loving and compassionate, why would he hide himself away? Why would he let people stumble in the dark when he could so easily enlighten them? There are many people who struggle with their faith, who are plagued by doubt, and who put themselves through mental anguish trying to make themselves believe; many of them ultimately become atheists. There are others who are all too willing to inflict the most horrendous suffering on their fellow human beings because of their beliefs. Why does God not put a stop to this? Just a few simple words from him could calm the doubts and fears of so many, put a stop to the religious violence that has spilled so much innocent blood, and give humanity a new shared purpose and an invincible source of hope. His absence, by contrast, allows crises of faith and religious warfare and bloodshed to continue unabated.
According to many religious traditions, the fate of those who die without believing in God, or believing incorrect things about God, is an eternity of torment and suffering in Hell. As any theist would agree, this is a horrible fate; and presumably God, if he is good and not evil, does not desire that anyone be condemned to undergo it. Why, then, does he not take all available measures to warn people? Does he consider it more valuable that people believe without good evidence than that they be saved from the fire by whatever means possible?
In reality, however, it is implausible to believe that any god worthy of worship would stand by and do nothing while a vast number of human beings marched toward damnation - or worse, that this god would then condemn them himself for making an honest mistake. It is implausible to believe that a loving creator would hide himself away and do nothing while his children wrestle with doubt and fear. Far more plausible, far more rational, is the conclusion that God's existence is not apparent because there is no such being in the first place, and never was. It follows as a consequence that the miracle-filled accounts of ancient history are not a reflection of reality, but an artifact of human credulity and ignorance - the farther back in time we go, the more willing people were to accept fantastic stories at face value, and the more difficult it was to test such claims even if anyone had wanted to. It also follows that the experiences of the divine people have today are not accurate perceptions of some deeper reality, but the result of wishful thinking and cultural indoctrination. But if I am wrong about this, I am willing to be corrected. As I write these words, I, along with many others, am standing on the edge of the highway. All it would take to persuade me to turn back would be one more burning bush...