brain vat presuppositionalist


brain vatIntroduction

Most of us who are active in discussions about religion will have come across a presuppositionalist at some point. These of course are people who argue that we must ‘presuppose the existence of God’ in order for things to make sense, and that presupposing the existence of God answers many questions. Those who have experience will have heard many questions from them, one such being the age-old question ‘how do we know you’re not just a brain in a vat?’. This is a question that they argue only belief in God can answer, and only belief in God can assure us that we are not. Before getting into the topic, we should first begin with a simple run down of what the ‘brain in a vat’ argument is for those who are not versed in the argument. So what is the ‘brain in a vat’ argument?

A Brain… In A Vat!

The ‘brain in a vat’ argument is a relatively simple one, and is designed to question our grasp of reality and what we can know about it. It asks us to imagine that all the we see, hear, smell, feel and know isn’t actually the result of sensory information coming in from ‘reality’. Instead of our senses getting information from ‘reality’, our sensory information is being fed to us by a super-computer. One that an evil genius, mad scientist, or overlords have attached our brains to. In fact, that is all we are, we are not these bodies that we inhabit, but simply brains, in a vat, attached by electrodes to a computer that feeds us information through our senses and fools us into believing that this is reality (Dupre, 2007). This, in essence, is the relatively simple concept behind the ‘brain in a vat’ thought experiment. It is an exercise in scepticism, but scepticism taken to the extreme. A thought experiment designed to introduce doubt to all that we know; and it is this problem that presuppositionalists say that only belief in God can give us any kind of answer to.

Unplugging The Brain

However, the problem itself has one glaring problem upon immediate examination. That is, what happens when the brain is unplugged from the machine? A brain on its own is just that, a brain on its own. With nothing powering it, it is simply an organ that sits there and does nothing. Without the brain, there is no mind, and therefore not ‘you’. Without a ‘you’ there is no reality for ‘you’ to experience. Think of the cow’s brain that we often see in something like a science class, or an exhibit. It sits there in a jar for us to observe, but it does not observe us. When we observe it we do not think ‘I wonder what that cow is experiencing?’ or ‘I wonder what reality is like for that cow?’. No, we usually observe it and think ‘cool, a cow’s brain in a jar!’. So would the question of what a lone human brain preserved in jar is experiencing even be a coherent one?

Of course it would not! The question of what ‘you’ would be doing if you were a brain in a jar is an even more incoherent question. This would mean that without being plugged into the machine that was serving you your experiences, there would be no reality for ‘you’. Which would mean that this would be reality. Knowing we were brains in a jar would not change what reality is like for us, it would only change our knowledge about reality. It would change our perceptions, our experiencing of reality, possibly even our behaviour, but nothing about the reality we are perceiving. The reality we are experiencing would still abide by the same laws of physics, we would have no more control over our reality than we do know. We would simply have an answer to a question, and some other questions like ‘how was the universe formed?’, and ‘do we have a creator?’.

If we were brain in a jar we would be brains in a jar having an experience, and we would hold knowledge about that. For some of us it may change our perceptions of reality, affect some of the philosophical questions we ask, or the way we interact with said reality, and only in that manner would our individual experience of reality change. Reality itself would stay the same. But what if we could change reality itself, such as bend the laws of physics, control gravity with our minds, or something else of that manner?

Physics brokenChanging The Laws Of Physics!

This, of course, would change reality. What we change would be an alteration of reality, and therefore a change of reality. Other’s would experience reality in an objectively different way. It wouldn’t be the individual’s reality that was affected, it would be a universal effect. Let us think about that for a moment though. If we were brains in a jar, hooked up to a supercomputer, controlling our reality, think of the technology that would take. The amount of knowledge that would take. The technical experience it would take to write that kind of software. Now think about the kind of ego it would take to ask that question.

Imagine the ego it would take to say that us, people who were created to be fooled by a computer program, could alter that program. For if a group of beings had the ability to create the illusion, they would have the ability, and ingenuity, to come up with a way to reinforce the illusion. Ways in which the illusion was enforced would be hard-coded into the software. It would be also be effortless to hard code into the software that we cannot change the parameters of the universe. It would be exactly as it is now. But what if the software, or the hardware, wasn’t up to scratch for the job?

broken-computerFaulty Hardware

Daniel Dennet makes an excellent point about this question in his book Consciousness Explained (1993). Here he makes the case that it would be more likely that reality actually exists (Dennet, 1993). The hardware necessary to run billions of brains in unison would be incredible. It also leads to other questions. Questions such as “what are new lives?”, “are they new brains hooked up to the system?”, or “are they new subroutines running?” If they are simply new subroutines, then what happened after the first generation died, and why did the simulation continue running? What is it running on and why did it need human brains to start? Why do I have thousands of generations before me, and yet I am the first brain?

Think of the technological and biological knowledge it would take to set something like that up. The wiring of the network to all the nerves that control our sensory input, converting whatever the machine is running into nerve commands and vice versa, to run the operating system it would take to run this kind of simulation, and the simulation itself. It seems more probable that a civilisation with that kind of technology could have perfected the technology. Even if they hadn’t, how problems with hardware affect the software. It would cause some kind of glitch, which would cause some kind of fault in the software, or complete shutdown of the technology. Complete shutdown would of course end the simulation, and the reality that exists inside of it would simply cease to function, and we would no longer be asking these kinds of questions. We would never know we were, and we would never know we ceased to be. What about a glitch in the software though?

bugA Bug In The Software

Could we ever truly know there had been a glitch in the software? For a civilisation with the knowledge to create this kind of simulation would have the ability to create a simulation that they could simply ‘rewind’. If the simulation was ‘rewound’ we would never know, and we would never know about the glitch in the system. This of course would take someone monitoring the code, or self monitoring code. The system would have to be under constant watch, everywhere at the same time in one form or another, in order for this to happen immediately. Even if the glitch wasn’t noticed immediately by the engineers or software, and the code to rewind it existed, we still would never know. For this moment that we are aware of could have been the moment it was ‘rewound’ to. This moment could be the reset. So we would still never know. It could still be before the rewind though, or perhaps the technology to rewind doesn’t exist.

Software Protection

This brings us back to the question of how well the illusion was coded. Surely the illusion could be created in such a way that we either do not accept the glitch in the illusion, or that we accept it and attribute it to something else. For those of us who hold the idea that the universe is entirely natural, we would challenge that glitch unless it was observed and measured in a way acceptable to the scientific method, and acceptable in an objectively studied or able to be studied objectively. There are many reasons we would not accept evidence of a glitch in the software.

For many believers, this glitch becomes attributed to their god, or their supernatural belief. Think of the existence of Jesus. Consider that Jesus was simply a glitch in the system. It was a localised event that took generations to get out to wider area. By the time it got out to the wider area it was a second-hand tale. As it has gotten older it has become less and less believed, and there were always those that simply rejected it. We even see around us that there are those who are, and always have been, active in questioning, casting doubt upon. It has also become so old that we can never really investigate it. If it was a glitch, then the illusion is so great, and written so well that it would always have been in doubt, and could never truly be shown to be true to a satisfactory standard of all that know of the glitch. The further away the harder, the harder to prove. This goes for proximity, which gets harder to believe the further the account gets from the observer.

It also seems less likely that in a natural universe that an event like the Biblical Jesus would occur, than it does that a glitch in a virtual world would occur. So, if the event of the Biblical Jesus did indeed occur, then it adds weight to the argument that we are brains in a jar living in a virtual world, than it does us living in a ‘real’ universe. Of course, it could also lend weight to the idea of God. That Jesus proves God exists, and that God existing proves this is real. Or does it simply lend more weight to the idea that we are brains in a jar living in a virtual world?

God Is Software Protection

In order to answer that question we need to return to some of our previous questions. The first one being the question of how would our perception of the universe change? In the case of some, their perception would change of course. Their behaviour may change as well, depending on their various other beliefs. However, what of the believer? How many believers are there that declare ‘nothing could change my mind about God’, or ‘nothing could change my mind about my religion’?

For these people, neither their knowledge of reality, nor their perception of it would change. For them, the only answer is that of God. This is not to say that all believers are like this, for there are those that would change their knowledge, and change their perception of reality. There are a huge amount, especially amongst Christians and Muslims, that would not. They would remain the same. They would even still be arguing against it, attempting to convince people who God is the answer, and that God proves we are not brains in jars living in a simulation.

Now back to the question of reinforcing the illusion, and keeping those in it in Here we have a belief, the belief in God, that not only would be useful in keeping people trapped in the illusion, we have a belief that causes people to refuse to accept that it could be anything else. Holding on to the belief in the face of inconsistencies, logically incoherent definitions, and the inability to actually test the idea. It is also a belief that encourages the holder to spread the belief, propagating itself. If all of this was indeed a virtual reality, and there was a need into fooling us that this is an illusion, God would indeed be a useful tool for those running the simulation.

Which leads us back to the idea of ‘software protection’. The effectiveness of the belief in God, especially by many Christians and Muslims, in convincing them they cannot be wrong about reality would make it ideal for protecting, and enforcing, the illusion. It is the type of idea we should expect to see in a system designed to protect the nature of the illusion from those perceiving it. The idea of God, and nature of some people’s belief, gives weight to the idea that it could be a virtual reality. One could argue here of course that God speaks to the believer, or that the believer feels God, but this too could be explained by a ‘software protection’ designed to enforce the illusion. However it is attempted to put God as the definitive answer to this question, it can be used to argue that it could also be an illusion.

extreme skepticExtreme Scepticism

The same extreme kind of scepticism could be held against any idea of reality. Questions continually asked, criticisms continually made, and ideas of illusion continually reinforced. God may offer an answer to the question, but it is an answer no more satisfactory than any other. There are of course other similar arguments of extreme scepticism, such as the ‘mischievous demon’ outlined in Descartes Meditations on First Philosophy (cite source). The same and similar objections can be raised about them, and many rebuttals already exist for these arguments. Rebuttals that do not involve the invoking of God. So the claim that only God can give us an answer to solving the problem is not one of truth. So how do we offer a rebuttal to the brain in the jar?

A Rebuttal To The Brain In The Jar?

How do we tell the difference between a virtual reality designed to fool us into thinking it’s real, and an actual reality? We only have experience of this place we exist in, and no other. We have no other frame of reference that we can compare it to so we could say ‘no, this is what a reality is supposed to be like’. Any civilisation advanced enough to create an illusion such as this also has the ability to enforce the illusion inside the system. The only way we would ever know we were simply brains in a vat living in a virtual world is if the technology was faulty or if the ability to know was part of the virtual reality. The chances of the hardware or software being faulty is slim, for a civilisation capable of this kind of technology would surely be capable of creating the hardware or software necessary to keep it running smoothly; and when faults did develop the simulation could easily be rewound, the faults or glitches erased from the memory of all those that inhabit it.

However, for all intents and purposes, this is reality. Even if we were brains in a jar living in a virtual reality, this is our reality. We can measure it, we can test it, we can interact with it; we live and die in it. To doubt that all the information we can gain from it is useless because we cannot know for certain that it is not x or not y, when clearly we have consistent results from our findings, and make advancements in technology and medicine, would be a pointless exercise. Assuming reality as a brute fact gets us places, rejecting all of that would mean a return to a state of nature. It would be a regression, rather than a progression. It also would mean very little to most people if they found out they were brains in a vat living in a virtual reality, as most would reject the premise and findings. Especially amongst the more religiously inclined. Spending a moment to reflect on how we would respond to someone who showed us proof we were brains in a vat should give us some idea of how little it would affect us.

There are good reasons to reject the idea of course. Why would a civilisation be inclined to create such a thing? What would the purpose behind it be? How are new brains attached, and what happens to the old brains? If there are 6 billion people on the planet, then where are these brains stored? And if not all the people living in this virtual world are the result of brains hooked up to a virtual reality, and these ‘virtual people’ fools us into thinking they are real, then this civilisation has the capability to just create a completely virtual reality, without the need for brains. So why does it use brains? Where does it get the power from to run the brains? There are simply far too many questions to ask, and answers necessary to support the premise, for it to be a reason to stop considering everything we experience to be ‘real’. Even for reasons of epistemology it is better for the premise to be rejected. For we cannot learn anything about this reality unless we accept that it is real, and we know what it exists because we exist in it, and we share experiences of it with others. There is no way to test for an existence outside of this reality, only infer it.


So in conclusion, while we may not be able to say with absolutely certainty that this is not a virtual reality, it seems far more probable that it is reality. It is also more productive to accept that it is reality, knowing it is not changes very little about our existence. It would only alter our knowledge and perception of it, rather than alter our reality as such. And though we cannot know with any certainty, neither can the believer who posits their God as the answer. It may give them assurances, and it may give them the false belief of being absolutely certain, but their argument does not hold any weight under deeper examination. If anything, it can be used to add weight to the idea that it is a virtual reality, and God is one of the methods through which the illusion is enforced.


Dennet, D. (1993) Consciousness Explained, London, Penguin Books Ltd.

Dupre, B. (2007) 50 Philosophy Ideas You Really Need To Know, London, Quercus Editions Ltd.