Puzzling that human beings should innately have the capacity to 'believe' that something invisible exists. This same criterion could be used in support of insanity as well, so it is not an exclusive argument, how could it be? There is no truth available here since we exist in 'plurality'. The big problem with the question is what is religion itself and that question is never answered or asked. Religion for most people seems to be an appeal for 'comfort seeking', G_d please save me etc. etc. etc. To some, it is used as a bulwark against the terror of 'non-existence'. However for a small minority, it is neither, Religion is rather a source of humility before the rampant power of the human ego coupled with a source of hope in the face of nihilistic hopelessness, born from a sense of powerlessness which is only the death froze of ego. No wages, salvation etc. in support of these maxims are sought, it simply seeks alignment with the larger 'direction' of the system, which includes all human endeavor scientific, mystical, philosophical etc as one w-holistic enterprise of humanity against the perceived nihilistic truth that channels us in-spite of our efforts. This awareness has no room for 'human' impostors created for lazy individuals who have no capacity for the awe necessary to confront their own humility when faced with the infinite, nor the ability to stand in the face of the immensity and still maintain hope. To accept suffering as the basis of truth and not falsity, using our compassion to serve hope rather than despair. Where life is equal to death in the immensity of the all, and where truth can be sought in the struggles of a fly caught on flypaper equally with the atrocities of Auschwitz.
Given this immensity; religion becomes struggle and our myths document that struggle, our innate ability to cognate such systems allows us to awaken to our responsibility, and humility in the face of immensity and hold our heads high in the face of all the suffering, maintaining hope not by false fairy-tales but rather with the recognition of the ALL and the OTHER. This recognition leads us to the simple 'unity' that is G_d. There are only two possibilities Truth or Falsehood (existence or non-existence), they are obscured by our own pluralistic thinking. The truth is singular whereas falsity must be plural. This is the logical postulate that leads us to what G_d is; it is 'THE' truth, and it is our doom to search for it through the generations, not because it may be found (to find it would be a loss of our identity, since singularity would nullify individuality), but rather in the pursuit we would change ourselves to a wider remit than we ever thought possible. Unfortunately our concept of religion, which has very little to do with G_d truncates the glorious journey before it has begun, rather than turn us outward it turns us inward, clutching our 'illusions' of truth like ikons, which are raised high in support of the singular G_d, forgetting that if that were true, there would be only one banner and all conflict concerning it would disappear, and indeed no need to raise the banner at all. The truth of 'religion' is that it should become obsolete (borrowing from a Jack Lemmon film), but in trying to avoid that it raises ego to protect itself from dissolution, by dogmatism it bludgeons 'acceptance' using the same methods as the atheistic thug only far more cruelly through the weak human psyche. Capacity for the awe of G_d metamorphosed into supernaturalism and superstition.
G_d is invisible because the truth does not yet manifest in humanity, we are still locked in the realms of egoistic horizons, which seek to protect rather than emancipate. Nevertheless, it is still the cognate G_d that is the 'popper' of the probability curves of human endeavor, because without that cognizance we are doomed to egoistic destruction, with no brakes on falsity.
Religion should be an invitation to search rather than a bunker of illusory 'answers. It is for G_d to initiate the search and for religion to truncate it in power structures. Politics is our modern 'acceptable' religious creation, serving banners of ideology rather than truth and indeed the expediency of falsity lubricates its wheels. Together with modern economics based on 'vacuous' wealth, we are happy to accept illusion rather than reality because we are 'comfort seekers' - the worlds most popular 'religion'. This lengthy exegesis could go on and on, but one last thought.
The word for 'religion' comes from the Latin 'Religare' which originally meant to 'read over' or study, it was changed by the early Christian church to mean 'bind to' and that has operated ever since. The simple meaning of words, when forgotten leaves their 'husks' behind' to dominate our consciousness and limit our horizons. However despite many 'religious' wishing to 'name' G_d and reducing the concept to husk he remains 'unnameable' in truth. So that just as G_d 'will be who He will be' we may one day 'be as we will be' in spite of ourselves, removing the fear of man, and emancipated from the 'husk' of our 'comfort seeking' illusions. Replacing them with humility and responsibility engendered by wider perspective, and what is wider than the ineffable 'concept' of G_d which of course is why it is innate in us all. It interesting to note there is no discussion of whether or not Santa Clause exists - but G_d still remains to be debated...
There are still no atheists in the foxholes - his 'name' still exists in the last desperate cries of the scared, or the 'ecstatic' - the orgasm still seems to release this cognate in acknowledgment in spite of ourselves...