Many of us are familiar with the “Brain in a jar” (also known as “Brain in a vat”) thought experiment. It talks about a hypothetical mad scientist who removes a person’s brain from the body, suspends it in a jar full of life-sustaining liquid, and connects its neurons to a computer which provides electrical impulses identical to those the brain normally receives (thank you Wikipedia for some of the words).
Thus the computer simulates some reality controlled by the mad scientist, while the poor person continues to have perfectly normal conscious experiences. Sort of what we saw in The Matrix Trilogy.
One of the direct conclusions from this though experiment is that (given the possible existence of such a mad scientist) you can never prove the actual existence of anything else but yourself. This idea, attributed to the French philosopher Rene Descartes (1596-1650), is quite interesting.
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Theorem: It is impossible to prove the existence of ‘God’ (using the religious definition).
Proof: Strictly from a logical point of view, there can be exactly two cases: Either ‘God’ exists or it does not.
If it does not exist, then its existence cannot be proven (because a true proof will imply its existence, while we discuss the case it does not exist).
If it does exist, then – by definition – it is also “almighty” (in human terms). The technological abilities of our mad scientist are therefore inferior to those of God, hence they are possible. So all our conclusions derived from the possible mad scientist’s existence – are also true. One of those conclusions is that you can never prove the actual existence of anything but yourself. Therefore, as a special case, you cannot prove the existence of God.
Thus in both cases above it is impossible to prove the existence of God. Quod Erat Demonstrandum.
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(This is adapted from my un-translated book “Games of Awareness”, 2012)