While perusing a social media discussion room, some atheists asked, “How do Christians know they are not brains in a vat?” They were discussing related issues with various Christians and were trying to get the upper hand in every sub-argument. They didn’t ask me to jump in (they knew that I debate atheists), so I mainly listened. Nevertheless, I believe there are problems with the question, which I will list here.

I presented several problems with the scenario listed below. But, before we start, we need to look at the difference between an internal and an external critique.

An internal critique examines the merits of an idea based on the internal consistency of the idea. Essentially it assumes the position being discussed and examines it for internal inconsistency or contradiction. By contrast, an external critique seeks to falsify an idea using criteria outside the initial idea being examined. So, for example, an internal critique of Christianity’s theology would require an examination of it to see if it is consistent within itself. An external critique of Christianity’s theology would be to examine it based on something like Islam or atheism. This is problematic because the reverse can be applied. Islam and atheism would be false based on Christian theology. So, external critiques are weak.

Nevertheless, let’s examine some reasons why the scenario has problems.

Indirect self-refutation

For something to be self-defeating, its premise is shown to be false by assuming its truth. For example, to say, “There is no such thing as truth,” is a self-refuting statement since if it is true, it is also false. It is directly self-refuting. But I will use the term “indirectly self-refuting” to refer to statements that are not self-evidently true and are also not based on what is evidently true.

• “indirectly self‐defeating, in the sense that our trying to achieve these aims may cause them to be worse.”¹https://academic.oup.com/book/12484/chapter-abstract/163161485
• The Philosopher Anthony Kenny argues that the idea, “common to theists like Aquinas and Descartes and to an atheist like Russell” that “Rational belief [is] either self-evident or based directly or indirectly on what is evident” (which he termed “foundationalism” following Plantinga) is self-refuting on the basis that this idea is itself neither self-evident nor based directly or indirectly on what is evident and that the same applies to other formulations of such foundationalism.”²https://en-academic.com/dic.nsf/enwiki/4920272

One: Invalid via the Christian Worldview

The idea that proposes the possibility that Christians are brains in a vat presupposes the existence of Christians. Christians derive their theology from biblical revelation. Biblical revelation teaches that God has revealed Himself to us within its pages, throughout history, and in the person of Jesus. Biblically, God has declared that we are born in human bodies, continuously live in human bodies (walking, talking, etc.), and die in human bodies, not in vats. Therefore, the brain-in-a-vat scenario does not work within the Christian worldview (internal critique). So the non-Christian who proposes the scenario is asking the Christian to abandon his worldview so he can attack his own worldview. This is an external critique and is invalid.

Two: Contradiction of retaining the Christian God’s existence

If the questioner wants to maintain the possibility that we are brains in vats, it does not negate the possibility of the existence of the Christian Trinitarian God. This would be problematic since the existence of the Christian God, per paragraph one above, negates the brain-in-a-vat scenario as being true.

Three: Inducing skepticism of itself

If it is the case that we are brains in a vat, could we know if it is true or not that we are brains in a vat since even the idea that we are brains in a vat can’t be trusted as being true? If the scenario were true, then to state, “I am not a brain in a vat, would be false.” But this would not be verifiable. On the other hand, saying, “I am a brain in a vat,” would be true. But, neither statement could be known to be true. Therefore, the scenario undermines its own premise since it induces skepticism about itself and indirectly refutes itself since it is not self-evidently true and is also not based on what is evidently true.

Four: Doubting our senses

If it is the case that we are brains in a vat, then it would mean that our senses (sight, sound, touch, smell, taste, and balance) are artificially induced. This means we can’t trust our senses, which casts doubt on the validity of the brain-in-a-vat scenario by undermining true knowledge of ourselves and reality. After all, if we can’t trust our senses, we can’t validate that our knowledge of the world is accurate. But, this also induces doubt about the scenario.

Five: Are our thoughts ours or programmed by someone else?

Furthermore, if we are brains in a vat and our senses are manipulated, then how do we know that our thoughts aren’t also manipulated – or at least wrong due to faulty sense input? This means we cannot trust our own thoughts, which further casts doubt on the brain-in-a-vat scenario. An idea that casts doubt upon itself is indirectly self-refuting since it is not self-evidently true and is also not based on what is evidently true.

If our thoughts are not freely ours because they are manipulated by external forces (i.e., external scientists), then even contemplating the idea of being a brain in a vat becomes meaningless since they are not our own thoughts but are manipulated and controlled thoughts. This means that given the brain-in-a-vat scenario, we cannot trust our thoughts to be rational, and asking the initial question becomes meaningless.

Six: Weakness of non-falsifiability

Falsifiability is “the logical possibility that an assertion, hypothesis, or theory can be shown to be false by an observation or experiment.”³https://dictionary.apa.org/falsifiability]  With the brain-in-a-vat scenario, how would anyone observe or show an experiment that can prove the assertion to be false? Generally, though not always, ideas that are non-falsifiable don’t correspond to reality. An example deals with the Heaven’s Gate cult in San Diego, which said that there was an alien ship on the far side of the Hale-Bopp comet that was coming to take them away. They had to commit suicide in order to be transported to the mothership. But, there was no way to prove this idea false. Therefore there was no way to prove it true. Its non falsifiability casts doubt on itself. Such doubts demonstrate inconsistencies in the scenario. Inconsistencies in the scenario imply indirect self-refutation since it is not self-evidently true and is also not based on what is evidently true.

Seven: Doubt due to possible non-existence of the questioner

If we are brains in vats, then that would imply that the person asking another person if he is a brain in a vat could be a figment of the imagination of the person being questioned – if it were true that he was a brain in a vat. But, if that is the case, then why would the imaginary questioner ask the question of the person who is a brain in a vat when the one questioned does not believe he is a brain in a vat? Is it a self-generated doubt about the one-who-is-questioned’s own reality? That would imply the one questioned is self-deceived. But how would he know he is self-deceived if, ultimately, his senses and the unreliability of his thoughts can’t be trusted? (See paragraphs four and five above) Furthermore, how would the questioner convince the one he questions that he, the questioner, is not a figment of the imagination of the person he is questioning? If the questioner says he’s not a brain in a vat, then that casts doubt on the brain-in-that scenario that he proposes could be true. If the questioner says he is a figment of the questioner’s imagination, then the questioner is saying that he is not real. All of this causes one to doubt the validity of the scenario by introducing doubt to its own validity. Such doubts demonstrate inconsistencies in the scenario.

Eight: The devil is deceiving you

How does the questioner not know that the idea of brains-in-a-vat is not a ploy by the devil to get people to deny reality, doubt knowledge, and ultimately deny God’s existence? If the questioner persists in constantly asserting (though invalidly, I might add) that every refutation does not falsify the brain-in-a-vat scenario, then how does he know that he is not being deceived by the devil into believing it is a logical possibility?

If it is fair for the questioner to ask the brain-in-he-vat question of the Christian (or anyone), then it is fair for us to ask how the questioner does not know that the Christian God has permitted her to be deceived by the demonic realm. If she says she doesn’t know, then she is admitting the possibility of the Christian God and the demonic realm. If the questioner denies the possibility, why the inconsistency? But, if she admits the possibility, then see paragraphs one and two above.

Nine: What must be the case for the brains-in-a-vat scenario to be false?

Is there any way to know if the brain in a vat scenario is false? If not, then there also is no way to know it’s true. Therefore the scenario casts doubt on itself since it is not self-evidently true and is also not based on what is evidently true. It is indirectly self-refuting. See paragraphs three, four, and five above.

Ten: What must be the case for the brains-in-a-vat scenario to be true?

If it is the case that we are brains in a vat, then what must be true in order for it to be a logical possibility? If the supporting conditions cannot be verified as true or are presently impossible, then the scenario is indirectly self-refuting.  So, let’s take a look.

1. This would mean that the brain-machine barrier has been bridged and that technology can now control us and deceive us completely. Welcome to the Matrix.
2. There must be sufficient technology that can sustain a biological brain with nutrients and mimic extremely complex sensory input.
3. This would mean that sense experiences like motion, momentum, pain, pleasure, lust, hate, watching movies, getting cavities, balance, taste, and me typing this article are all generated by a machine that can simultaneously imitate tactile awareness from my fingers, the pressure on my legs from sitting in a chair, hearing my heater turn on and off, watching my computer screen, feeling the desk fan blow on my right arm, all simultaneously such that I am unaware of any failures in the system.
4. It would mean that one or more scientists are doing some sort of experiment to see if they can maintain a brain, or brains, in a vat such that the subject is unaware of it. But to what end?
5. It would mean that such scientists have no ethical problem with invoking a monumental deception on human subjects and experimenting on them against their wills. After all, I do not want to be a brain in a vat. Would these scientists be evil or good or what?
6. But if that is the case, then the experiment seems to be a success. Why then continue? Is it because they lost my body somewhere, and I’m now stuck in a vat, and they have the ethics not to want to kill me – yet apparently approve of experimenting on people?  Nazis anyone?
7. Murder would be a viable option in the brain-in-a-vat scenario since the scientists could decide to end the experiment by turning off the power. Or would they put my brain back in my body (or a different body) so I am not aware of any change? Which would mean they would recreate the exact world I’m already in????

Conclusion

Given the reasons and arguments above, it is an empty challenge to ask us to disprove that we are not brains in vats. there are too many inconsistencies, unanswerable questions, and indirect self-refuting ramifications. Furthermore, the Christian worldview does not allow such deception to occur. Therefore, the questioner must ask the Christian to abandon his worldview in order to refute it. But, this would be an invalid external critique. So, the question “How do Christians know they are not brains in a vat?” ultimately has no merit.