The Truth was the presumptuous name of the religion, the faith that lay behind reality. It arose from the belief that what appeared to be real life must in fact - according to some piously invoked statistical certitudes - be a simulation being run within some prodigious computational substrate in a greater and more encompassing reality beyond. This was a thought that had, in some form, crossed the minds of most people and all civilisations. However, everybody quickly or eventually came round to the idea that a difference that made no difference wasn't a difference to be much bothered about, and one might as well get on with (what appeared to be) life.

The Truth went a stage further, holding that this was difference that could be made to make a difference. What was necessary was for people truly to believe in their hearts, in their souls, in their minds, that they really were in a vast simulation. They had to reflect upon this, to keep it at the forefront of their thoughts at all times and they had to gather together on occasion, with all due ceremony and solemnity, to express this belief. And they must evangelise, they must convert everybody they possibly could to this view, because - and this was the whole point - once a sufficient proportion of people within the simulation came to acknowledge that it was a simulation, the value of the simulation to those who had set it up would disappear and the whole thing would collapse.

If they were all part of some vast experiment, then the fact that those on whom the experiment was being conducted had guessed the truth would mean that its value would be lost. If they were some plaything, then again, that they had guessed this meant they ought to be acknowledged, even - perhaps - rewarded. If they were being tested in some way, then this was the test being passed, this was a positive result, again possibly deserving a reward. If they had been undergoing punishment for some transgression in the greater world, then this ought to constitute cause for rehabilitation.

It was not possible to know what proportion of the simulated population would be required to bring things to a halt (it might be fifty percent, it might be rather smaller or greater), but as long as the numbers of the enlightened kept increasing, the universe would be constantly coming closer to the epiphany, and the revelation could come at any point.

The Truth claimed with some degree of justification to be the ultimate religion, the final faith, the last of all churches. It was the one which encompassed all others, contextualised all others, could account for and embrace all others. They could all ultimately be dismissed as mere emergent phenomena of the simulation itself. The Truth could too, in a sense, but unlike them it still had more to say once this common denominator had been taken out of the equation.

It could also claim a degree of universality that the others could not. All other major religions were either specific to their originating species, could be traced back to a single species - often a single subset of that species - or were consciously developed amalgams, syntheses, of a group of sufficiently similar religions of disparate origin.

The Truth, claiming no miracles (or at least no miracles of proof) and being the work of no invdividual, all-important prophet was the first real post-scientific, pan-civilisational religion - or at least it was the first that had not been simply imposed on reluctant subjects by a conquering hegemony. The Truth could even claim to be not a religion at all, where such a claim might endear it to those not naturally religious by nature. It could be seen more as a philosophy, even as a scientific postulate backed by unshakeably firm statistical likelihood.

There were some potentially unfortunate consequences implicit in a profound belief in the Truth. One was that there was a possibility that when the simulation ended, all the people being simulated would cease to exist entirely. The sim might be turned off and everybody within the substrate running it would die. There might be no promotion, no release, no return to a bigger and better and finer outside: there might just be the ultimate mass extinction.

Also, back in the (apparently) real world, there was an argument that the Truth implied approval of its own extinctions, that it tacitly encouraged mass murder and genocide. Logically, if one way of upping the proportion of those who truly believed was to evangelise, convince and convert, another was to decrease the numbers of those who steadfastly refused to accept the Truth at all - if necessary by killing them. The tipping point into revelation and deliverance for all might come not at the moment when a sceptic became a believer but at the point that an unreformable heathen breathed their last.

Excerpt from The Algebraist, by Iain M Banks. Edited slightly...