I think therefore I am: How far can we doubt our existence?

How do you know you exist? To what extent can you doubt you exist? Rene Descartes compels us to explore the idea of doubt in a way that lets us question the knowledge of our existence. In his meditations, he introduces us to a certain kind of inquiry where he has us doubt everything that we could possibly doubt— whether it’s the validity of our senses or the already preconceived knowledge we have about our existence. Descartes’ starting point of inquiry is to see whether there’s anything he can’t doubt. And the one thing that he can’t doubt and know for certain is, the fact that there is thinking and doubting occurring. So for Descartes,  the subject of the thinking and doubting becomes the main thing being inquired about– an I that thinks and doubts, hence leading to one of the most groundbreaking philosophical statements, “I think therefore I am.” 

In Meditations, Descartes gives us doubting as a potent philosophical tool. A way of getting to the utmost certain truth that we could possibly arrive to. In his book, Descartes takes us on a philosophical train of doubting everything we know as he tries to land us to something that can’t be doubted. He does this by having us doubt our senses, perceptions and beliefs. Through this inquiry, he makes us consider the possibility of an evil demon that deceives him and causes him to doubt everything. He writes: 

"I will suppose, then, not that Deity, who is sovereignly good and the fountain of truth, but that some malignant demon, who is at once exceedingly potent and deceitful, has employed all his artifice to deceive me; I will suppose that the sky, the air, the earth, colours, figures, sounds, and all external things, are nothing better than the illusions of dreams, by means of which this being has laid snares for my credulity." 

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Descartes is essentially trying to demonstrate that it is possible to doubt everything we believe to be true, including the evidence of our senses, but still be left with something we can’t doubt: that there is doubting happening. By creating a hypothetical scenario in which everything we perceive could be an illusion, he is trying to establish a certainty for a knowledge based on the one thing that’s certain, the existence of doubting and a subject of the action. Descartes is saying that the fact that there’s something there to doubt means there must be something that is doubting.

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“And yet firmly rooted in my mind is the long-standing opinion that there is an omnipotent God who made me the kind of creature I am. How do I know that he has not brought it about that there is no earth, no sky, no extended thing, no shape, no size, no place, while at the same time ensuring that all these things appear to me to exist just as they do now?”  

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But how far can doubt take us? Senses, perceptions and even beliefs are all prone to doubt for Descartes. But can one also doubt the notion of a subject that is doing the doubting? Just because there is doubt, does it necessarily imply the existence of a thinker or a subject of the doubting? Surely, just like the other mental phenomenons, the subject of the doubt could also be a product of the brain's ongoing activity. If we’re not supposed to take anything as a presupposition and question everything, why should we presuppose a thinker or a subject that is doing the thinking. The inquiry doesn’t have to stop at the certainty of I but rather, one can doubt the very notion of one’s existence as a subject and the possibility that they could be mistaken about its existence. In the second meditations, Descartes tries to understand this subject or I:

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“But what then am I? A thing that thinks. What is that? A thing that doubts, understands, affirms, denies, is willing, is unwilling, and imagines and has sensory perceptions.”   

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 By defining the self as a "thing that thinks", Descartes is suggesting that the essence of the self lies in the ability to think, reason, and perceive. He also lists other mental faculties such as doubting, understanding, affirming, denying, willing, and unwilling, which he believes are all necessary attributes of the self. In other words, he believes that there must be something that is doing the thinking, and that this thing must be a subject or an "I."  

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However, it’s necessary to doubt the very notion of a thinking thing if we’re attempting to arrive to a certain truth. Especially, if we’re not supposed to take anything as a presupposition and question everything- why should we presuppose a thinker just because there is thinking. The assumption that thinking requires an existing subject could be doubted entirely in the same way the thinking could be doubted. This is a radical leap, but Descartes lays out the brick stone for this philosophical inquiry, so we must act as if we’re Descartes and see if we can further doubt the existence of this self.  

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Descartes might argue that even if we doubt the existence of a thinking subject, we cannot doubt the fact that there is thinking occurring. Even if we doubt the self who is doing the thinking, we cannot doubt the thoughts themselves. This means that there must be some sort of existence behind the thoughts, even if we cannot be sure what it is. Descartes states:  

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“The fact that it is I who am doubting and understanding is and willing is so evident that I see no way of making it any clearer.” 

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It could be argued though that the  assumption that there must be a subject or an "I" behind the thoughts is just that - an assumption. The experience of thinking itself can arise without a thinker, and the sense of there being a self who is thinking could also just be another thought or mental construct. In this view, the experience of thinking itself is simply a natural phenomenon, like the weather or the movement of the stars.

From a linguistic approach, we can also doubt the existence of  "I" as a “thinking thing” to be a mere linguistic construct, rather than a real, existing entity. In other words, a product of language and social conditioning. This is because, when we say "I," we are referring to a collection of experiences, memories, and thoughts that we have accumulated over time. In other words, we’re using language as a tool to create a sense of identity and meaning around experiences, memories, and thoughts which constantly change and evolve. Furthermore, we use language to construct these mental images of ourselves, which we then believe to be our true self thus creating the notion of a subject. And this same inquiry proves that the one who is doubting the thing and is posited as a separate subject or thinker behind the thoughts and doubts can also be doubted.

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