In an e-mail, a friend recently asked:
Why is knowing the truth always better than living with an illusion? What if the illusion is that there is no god and the truth is that there is a mean, unfair, spiteful god? What is wrong with living in a illusion? What makes something an illusion anyway?
I think it would be better to speak in terms of delusion rather than illusion. Illusions are shortcomings in perception, while delusions are shortcomings in belief. One can perceive an illusion— for example a desert mirage— and even hypothesize that the perception indicates water in the distance. This is not delusion. But when one develops the fixed, false belief that water in the distance magically dries up when approached, even when presented with evidence to the contrary, then the individual is under sway of a delusion.
Illusions are natural and common— they can even be fun, as when learning about optical illusions or enjoying a stage magician. Delusions, however, are a form of mental illness. Just as physical illness prevents a person from engaging fully with the world on a physical basis, and just as physical health and fitness are highly prized and considered necessary prerequisites for many important activities, mental illness prevents a person from engaging with the world on a cognitive and emotional basis. Mental health, including freedom from delusion, is highly prized because it is a prerequisite for fruitful human interaction and cooperation— successful parenting, for example.
Sure there are cases where artists have produced arguably more interesting work when psychotic, but to the extent that these people are “broken from reality,” they are also unable to function within society.
Science itself is founded upon the idea that it is possible to discover great and useful truths by systematically identifying and avoiding the many cognitive biases and fallacies to which the human mind is susceptible.
Religion, on the other hand, is essentially institutionized delusion. It plays directly upon major fallacies to propagate its ideas. Here are a few common examples:
Furthermore, every major religion places certain ideas and events beyond the realm of rational inquiry. They are articles of faith, and are to be accepted by adherents without question. This approach to knowledge is antithetical to the desire to live free from delusion.
Crucifixion, artist unknown
Finally, religion holds a static, unchanging view of the universe and humanity’s role within it. On this view, all that humans need to know has been handed to us by divine authority, and human attempts to discover more are at best considered amusing attempts to reflect divine nature, or at worst self-aggrandizing and dangerous attempts to subvert divine authority. Religion admits of making no mistakes, at least where dogma is concerned— if the evidence conflicts with the articles of faith, it is the evidence that is suspect. Science, on the other hand, continuously tries to prove its best theories wrong, and in doing so, replaces them with better theories. This is an active, dynamic, and participatory approach to understanding reality.
I think the only part of your question I have left unaddressed is, “What if the illusion is that there is no god and the truth is that there is a mean, unfair, spiteful god?” In this case, I would still want to know the truth, rather than hold some form of delusional atheism. I would want to understand why God is mean, unfair, and spiteful. I would want to know whether there was some way of changing his view, or at least avoiding the suffering likely to be caused by such a view. As an atheist, I stoically accept death as part of life. In the hypothetical you pose, I would also stoically accept the reality of God.