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What determines a person’s existence?

(Image Description: Cover image is an older painting in black and white of French Philosopher Rene Descarates, a man with dark, long, curly hair, with a slight mustache and a white collared shirt with a dark jacket on top of the white shirt.)

It is often assumed that a single human body is a single person, but not everyone agrees. Plurality is often defined as the state of multiple people residing within the same body.

Rene Descartes, a philosopher famous for his skepticism, entertained the idea that everything we think and experience “could have all been put in our minds by the Evil Genius who created an illusory world so seamless, we’d have no way of detecting the illusion” (Tallman). This is similar to skepticism about plurality, except instead of a hypothetical Evil Genius, there is the idea that the brain itself may be creating an illusion of existence. Descartes could doubt “everything except the fact he was doubting,” meaning that “he must exist—at least as a thinking thing” (Tallman). He said that ability to think, and especially doubt, is what defines the existence of a mind. It is common for people to doubt their plurality. While this reasoning doesn’t apply to questioning the existence of others, the doubter themself must exist in some form.

Nathan Day, in his guest article for Ex Uno Plures, a website focused on plurality, says that “It seems absurd to say that a machine made of neurons cannot run multiple operating systems the same way that a machine made of wires can.“ (Day). I agree with Day's statement because the human brain is considerably more complex than any of today’s computers, and is capable of containing many different beliefs and thoughts within itself, even conflicting ones. It makes sense that it could contain multiple minds with their own thoughts, beliefs, and sense of self. “In the end, I’ve got a set of options: I can become one again… Or, regardless of how, when, or why I’m multiple, I can simply continue to be so” (Day). While I agree that it is good to practice a certain level of skepticism, I also agree that you should remain open-minded about what your experience and reasoning lead you to. You shouldn’t struggle to conform to society’s idea of “normal” if that is not your truth.

Descartes and Day have similar positions, with Day even referencing Descartes. Descartes “couldn’t know if he had a body...But he must have a mind, or he couldn’t be having these thoughts” (Tallman). His body may have been an illusion created by the Evil Genius, but that didn’t detract from his mental existence. Day agrees, saying that “We’re so used to seeing “people” as beings having faces like ours… that we’ve confused the form and the function” (Day). They both agree that a person’s existence can be derived from purely mental characteristics, such as an ability to doubt or sense of self. A body may be a pretence, or even an illusion, that is independent to the person, or people, it belongs to.

Descartes and Day have similar ways of proving their existence, and I agree with them both. I believe that if you can consider your own existence, whether with certainty or doubt, that would mean you’re real. Since someone can prove their existence regardless of their body’s, I believe that sharing a body does not detract from one’s personhood. Something Descartes and Day overlooked was that someone could be unaware of the possibility they may exist. Descartes’s “I think, therefore I am” can be applied in a broader sense. If someone has thoughts of any kind, they are a real person, even if they don’t have a body of their own that you can see.

Works Cited

Day, Nathan. “Personhood and Identity.” Ex Uno Plures, 2009,

Tallman, Ruth. Cartesian Skepticism - Neo, Meet Rene: Crash Course Philosophy #5. YouTube, CrashCourse, 7 Mar. 2016,

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