Imagine a type 2 civilization on the kardashev scale where our knowledge has advanced so much that nothing known to science can destroy it. Any traces of material arguing about the creation/origin/meaning of life/afterlife that lacks credibility are purged and lost forever, in this universe religion is a taboo. By genetically modifying the structure of dendrites and axons of the brain, signal is transmitted via luminescent instead of electrical current through a conducting fluids therefore greatly improve overall brain performance. I'm not saying religion is the theater of war nor claim it leads to downfall of a civilization, I wonder by removing the fear of the unknown and remove all supernatural elements from the equation could this result in civilization that is truly immortal?
closed as primarily opinion-based by MichaelK, JDługosz, Mołot, Hohmannfan, kingledion Nov 24 '16 at 13:20
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Theistic Religion or All Religion?
To make it simple, if we would come to a point where nobody would believe in any kind of deity, we would simply have one reason less to kill each other, but as history shows, Religion is by far not the only reason to grab a weapon. So at least in this way, that civilization wouldn't differ that much from us, maybe a little less aggressive towards the different but not that much that it actually would matter.
However an absolute Religion free world would be a mind free world. Because Religion is a specific fundamental set of beliefs and practices generally agreed upon by a number of persons or sects and that can be anything, even a group dogmatically agreeing that a certain cereal is the best cereal above every other cereal. And you won't stop that as long as someone still can think.
Consider the purpose of religion in a scientific world
Religion initially comes under a heading of coping with the unknown, in the long term it's redundant in this role as it is displaced by science learning about the unknown so it's no longer unknown and moves into a different position in our lives maintaining community and identity.
In the Western world many people who have religion as an identity never attend a place of worship, they never pray, they don't believe in god. The religion is their background, it's who they are and where they come from. It's a part of maintaining a personal identity in a world where it's all too easy to become anonymous, saying "I'm part of this small distinct group". An upsurge in religion is entirely understandable, even in our very scientific world, when you consider it as part of our very human urge to belong.
Never ask a man if he's from Yorkshire: if he is, he'll tell you soon enough; if he isn't, it'll only embarrass him.
In a civilisation that has achieved type 2, this will be the primary purpose of religion. Consider the scale of a society that has achieved that level, and the struggle to maintain an identity within those masses, something to say that "I am unique" within this vast sea of people. Religion gives a culture that you're born to, a set of customs that set you apart from the masses of the worlds and mark your membership of a smaller group that Dunbar's number is more capable of understanding.