How to Defeat the Cartesian Demon

What if an evil demon is deceiving us into thinking the world and everything around us exists, and it’s all really a hallucination? 

It was French philosopher and mathematician René Descartes who first introduced this idea in his book Meditations on First Philosophy. In this philosophical exploration, he invites readers to participate in a thought experiment that questions the reliability of our senses and perceptions, making us question if what we call reality really exists.

If I said I was never unsettled by the idea, I would be lying - I was quite disturbed when I first read the passage. A fear that was only furthered when I watched The Matrix for the first time, and read about the more modern version of the evil demon: the brain in a vat theory (which holds that we are just brains in a jar, being fed electrical pulses that deceive us into thinking external reality is the way we perceive it). 

I think the core of the fear lies on the fact that we cannot conclusively prove that we are not brains in vats, humans in The Matrix, or victims of the Cartesian Demon. 

However, these fears disappeared after I was introduced to epistemology as conceived by philosophers Karl Popper and David Deutsch. Hence, today, my aim is to show how a better understanding of the nature of knowledge allows us to be liberated from these fears (which I will call explanationless fears).

The first step is to acknowledge that what is feared (in this case, being brains in a jar) can be logically and physically possible. If it was the case that we were humans in the Matrix (and it seems that it could be the case), it is a reasonable thing to fear. After all, it would imply that all we have been living and experiencing is an elaborate lie.

That being said, let me now introduce the main claim of today’s entry: In the absence of an explanation of how they will come to be realized, physical and logical possibilities provide insufficient reason for us to entertain them.

This means that when a fear is grounded on nothing but a mere physical or logical possibility, there is no reason for us to keep that fear: after all, it’s an explanationless fear. In our example of the Cartesian Demon, it means that although it could be the case that we are brains in a vat, unless we experience or observe anything suggesting that to be the case, the fear is irrational. 

Some might object saying that rather than dismissing the fear, we should simply stay neutral: there is no reason to prefer the idea that reality exists over the idea that reality is an illusion. 

This I also disagree with, for there are reasons to prefer the former over the latter. 

The former idea (that reality is not an illusion) explains all the phenomena we experience in the world without leaving any residue. However, the latter idea (that it is all an illusion) needs to invoke the presence of entities whose existence we have zero reasons to even suggest in the first place (let alone believe in!). For instance, it requires invoking an evil demon or an evil scientist deceiving us (not to mention that the idea also raises many questions such as why they are tricking us, etc.). 

In a way, the rejection of the explanationless fear is grounded on Occam’s Razor: we should not multiply extra entities unless necessary–there is no reason to bring up a theory invoking an evil demon if there is nothing suggesting that such an entity exists. 

This can, of course, be extended to many other explanationless fears that plague people’s minds. It can dispose of solipsism, because although it could be the case that I’m the only person with a mind, there is nothing suggesting that to be the case. It can also dispose of fears about AI scientists being “on the verge” of creating AGI (artificial general intelligence, capable of everything a human being is capable of, including consciousness)–we don’t even have a theory of how consciousness arises in humans, meaning there is nothing in the world that could suggest we’re getting ‘closer’ to AGI. Finally, it can also help with emotional fears such as the fear that someone who loves us has suddenly stopped loving us–in the absence of observations that indicate the love has ceased, a mere physical or logical possibility is not enough to ground a fear. 

I admit the line is not always clear of what constitutes observations that pave the way for a physical or logical possibility to be realized. However, I strongly believe that once we realize that possibilities are not enough, we will start to examine our fears more critically–allowing us to get rid of those explanationless ones that don’t deserve our attention.