God is probably an illusion.

The existence of God (i.e., an omniscient, omnipotent, and omnibenevolent God) is improbable on both evidential and a priori grounds. This assertion is supported by two basic contentions. Firstly, the suffering resultant from animal predation and natural selection is much better explained by naturalism than theism. Secondly, the hiddenness of God and the weak evidence surrounding theism actually represents the foundation of a strong atheistic proof. When these two arguments are combined and viewed in light of the absence of evidence for God, they provide a strong cumulative case for atheism.

C1: The Evidential Argument From Evil

The predictive power of metaphysical naturalism to account for natural evils makes atheism objectively more likely to be true than theism. Consider, for instance, the clumsiness with which evolution has assembled all living organisms. The development of life on Earth was engineered by natural selection – a mechanism that has left 99.9 percent of all of the species that have ever lived on Earth extinct. [1] Likewise, the struggle for survival in nature guarantees that most animals (human and nonhuman) will suffer horribly as they get outcompeted for resources and die from lack of sustenance or from being eaten. In a very real way, evolution is advanced by the grinding of teeth upon bone. Moreover, even if any creature can avoid being preyed upon, they will still suffer and languish in their old age. Of course, all of this suffering is much more likely to occur given naturalism than it is given theism. Thus, all things being equal, naturalism is a much better and more parsimonious hypothesis than theism.

Paul Draper takes this theme and uses it to create his version of an argument from evil. It is slightly divergent from other arguments from evil, but it still touches upon the same key points. And he bases his argument on the following evidence statement:

E: For a variety of biological and ecological reasons, organisms compete for survival, with some having an advantage in the struggle for survival over others; as a result, many organisms, including many sentient beings, never flourish because they die before maturity, many others barely survive but languish for most or all of their lives, and those that reach maturity and flourish for much of their lives usually languish in old age; in the case of human beings and some nonhuman animals as well, languishing often involves intense or prolonged suffering.

P1: We know that E is true.
P2: Naturalism has much more predictive power with respect to E than theism does (i.e., E's truth is antecedently many times more probable given naturalism than it is given theism).
P3: Naturalism is more plausible than theism (i.e., naturalism is more probable than theism independent of all evidence).
C: So, other evidence held equal, theism is very probably false. (Draper [2])

Naturalism is, by its very nature, a simpler hypothesis than theism, and it has at least the same explanatory scope as theism (i.e., there is no observable phenomena which must necessarily be subject to a supernatural explanation). Of course, simple explanations are inherently more plausible than complex explanations. [3] Ergo, the weight of the evidence regarding natural evil points strongly to the truth of naturalism. While it is possible that a God – for reasons unbeknownst to humans – has morally sufficient reasons for allowing such a barbaric system of creation, it is highly unlikely given the predictive power of naturalism to account for natural evils. In light of this data, theism is very likely to be false.

C2: The Argument From Divine Hiddenness

The hiddenness of God from human perception provides strong grounds to suppose that the God of theism isn't actually real. For example, if God wanted humanity to know that he existed, as many theists often propose, then he should have brought about a situation whereby everyone reasonably believed in him. Therefore, if God existed and wanted us to know this, then reasonable nonbelief should not occur. But reasonable nonbelief does occur because God has refused to provide any compelling evidence that he exists, if he does exist. In other words, the central concepts about God's nature necessarily entail a contradiction.

John Schellenberg was one of the original pioneers behind the argument from divine hiddenness. And he surmises this argument in the following syllogism:

P1: If there is a perfectly loving God, all creatures capable of explicit and positively meaningful relationship with God who have not freely shut themselves off from God are in a position to participate in such relationships--i.e., able to do so just by trying to.
P2: No one can be in a position to participate in such relationships without believing that God exists.
P3: If there is a perfectly loving God, all creatures capable of explicit and positively meaningful relationship with God who have not freely shut themselves off from God believe that God exists (from 1 and 2).
P4: It is not the case that all creatures capable of explicit and positively meaningful relationship with God who have not freely shut themselves off from God believe that God exists: there is nonresistant nonbelief; God is hidden.
P5: It is not the case that there is a perfectly loving God (from 3 and 4).
P6: If God exists, God is perfectly loving.
C: It is not the case that God exists (from 5 and 6). (Schellenberg [4])

Of course, there are some who argue that free will would be compromised if every single person actually did believe in God. But this objection cannot be valid – for there are certainly ways in which an omnipotent God could reveal himself to the world so that every person capable of believing in him actually did believe in him. Surely, a sufficiently persuasive display of magical powers from a deity would be enough to convince any skeptic. As a result, God's failure to reveal himself clearly and unambiguously provides strong grounds to conclude that he isn't real.

As can be plainly seen, the presence of reasonable nonbelief presents a very real problem for the existence of God. Another common (and irrelevant) response to this argument usually alludes to the notion that the ways of God are mysterious. However, this proposition is entirely contrary to the central doctrines surrounding theism. According to theism, God wants humans to have a relationship with him. Meanwhile, this God has also cloaked himself from the greatest tools and insights of modern science. Surely, any God that would bother to involve himself in the affairs of one primate species in a universe teeming with over 70 sextillion stars is not as inscrutable as all that. [5]

::Conclusion::

Given the paucity of evidence for theism and the strong evidential grounds for atheism, the God hypothesis is simply untenable. As was demonstrated earlier, naturalism has more predictive power than theism in accounting for evils that can be found in nature. Consequently, the occurrence of natural evils makes it reasonable to doubt the truth of theism. Moreover, the hiddenness of God provides an equally compelling reason to suppose that theism is erroneous. In short, no one is in a position to love God if they remain convinced that he isn't real. Likewise, it is a very strange sort of loving God, indeed, that would set up an arbitrary salvation scheme in which an accident of a person's birth would largely determine their fate for eternity. Therefore, on balance, the weight of the evidence leans heavily in favor of the proposition that God is an illusion.

Sources:
1. http://www.lassp.cornell.edu...
2. http://www.infidels.org...
3. http://plato.stanford.edu...
4. http://www.infidels.org...
5. http://www.space.com...