Descartes and the Certainty of Self-Awareness

To what extent can we trust the information that comes to us from our senses? Where are the limits of our knowledge? To answer these questions, we examine the ideas of Descartes.
Descartes and the Certainty of Self-Awareness
Matias Rizzuto

Written and verified by the philosopher Matias Rizzuto.

Last update: 09 February, 2023

René Descartes (1596-1650) was a prominent scientist who also made important contributions to the field of philosophy. For him, the philosophical methods used by his contemporaries were wrong. His vision was opposed to those who maintained that knowledge could be obtained through the senses. Therefore, he tried to find some kind of certainty to help him advance on the path of knowledge.

For Descartes, all knowledge must be deduced by reason. For this reason, his philosophy was called rationalism. In effect, he tried to transfer the method of mathematics to philosophy. Starting from simple but sure truths, he tried to build a solid and unquestionable kind of knowledge.

Doubt as the foundation of certainty

To fulfill his mission, Descartes decided to isolate himself from the world and systematically question all the beliefs, opinions, and truths that, up until that time, he believed to be true. In fact, he examined, via ‘methodical skepticism’, everything he’d believed up to that moment.

Descartes warned that information that we take for granted often comes to us through our senses. On the other hand, our senses can easily deceive us. For example, if you introduce a stick into the water, it appears to break. However, what really happens is that your eyes are deceived by the effect caused by the light on the water. In the same way, you might see a column in the distance and think that it’s round but, as you get closer, you realize that it’s actually square.

man thinking
Descartes believed that knowledge must be deduced by reason, hence his perspective is known as rationalism.

Our senses deceive us

These considerations led Descartes to believe that, if our senses deceive us, we can’t trust the information that comes to us through them. That said, there are certain things about which we can’t really be deceived. For example, it’d be hard for me to doubt that I’m sitting, at this precise moment, writing this article.

Despite this fact, we do sometimes dream of situations that seem so real that we believe we’re living them. But, when we wake up, we realize that they were just the products of our imaginations. Consequently, Descartes concluded that we can’t trust the information that our senses provide us.

“The senses deceive from time to time, and it is prudent never to trust wholly those who have deceived us even once.”

-Rene Descartes-

An evil genius?

There’s some knowledge it makes no sense to doubt. For example, mathematics. For instance, whenever we add two plus two, four will be the result. That said, Descartes took doubt to the extreme, and wondered what’d happen if, instead of a god, there was an evil genius who led us into error every time we added two plus two.

This last argument may sound rather far-fetched. But, you must consider the historical context in which Descartes lived and understand that he didn’t want to arouse the attention of the Inquisition. Indeed, admitting that God, who was supposed to be pure goodness, could be intentionally deceiving us could well have been taken as heresy.

The only certainty is self-awareness

Through methodical doubt, Descartes destroyed the idea of all knowledge being possible. So, stripped of the senses and mathematical truths, where could certainty find refuge?

In fact, the intrepid philosopher realized that, even when he doubted everything, there were still mental processes at play. For instance, he couldn’t doubt the fact that he was thinking. It was at this point he gave shape to one of his most emblematic sentences: cogito ergo sum, that is, “I think, therefore I am”.

We can doubt everything we see, even what we think, but we can’t doubt that we’re thinking. Moreover, if we’re thinking it’s because we’re existing. For this reason, our only certainty is self-awareness. We’re aware of ourselves because our intellect can clearly and distinctly perceive this fact. “I am merely a thinking thing,” Descartes declared.

Some of the attributes of this thinking thing or substance are feeling, wanting, imagining, and knowing. In fact, in order to advance in knowledge, we must analyze the mental contents that inhabit thought.

“I am a thing that thinks, that is, a thing that doubts, affirms, denies, understands a few things, is ignorant of many things, is willing, is unwilling, and also which imagines and has sensory perceptions.” 

-Rene Descartes-

Mind with a man inside
Our only certainty is self-awareness

Descartes’ ideas

Descartes differentiated the knowledge that originates in our intellect from the kind that comes from our senses. In addition, he called the contents that appear in our minds ideas. He distinguished at least three main types:

  • Adventitious ideas. Those that come from abroad.
  • Factitious ideas. Those produced by us.
  • Innate ideas. Those that don’t come from abroad or are produced by us.

While adventitious ideas are the sensory impressions of the objects of the external world, factitious ones are those that we build with our imaginations from other ideas. For example, the idea of a centaur. However, there are certain ideas in our minds that don’t seem to come from outside or have been created by us. For instance, the ideas of infinity and perfection.

Are we alone in the world?

We’re limited and finite beings. So, how could we have created the ideas of perfection and infinity ourselves? On the other hand, if we were perfect beings, we wouldn’t have any doubt because we’d lack nothing and would know everything. These ideas can’t come through our senses either, since nothing exists in the perfect and infinite world. So, where do they come from?

Here, Descartes used an argument to prove the existence of God. It was criticized by many later philosophers. Descartes argued that these ideas must’ve been placed into us by some kind of perfect, infinite, and limitless being. Since goodness is part of perfection, a being with such characteristics couldn’t deceive us. With this, the evil genius hypothesis fails, and the kind of certainty of mathematical truths prevails.

The certainty of the sensible world

If we accept Descartes’ proof, God couldn’t have created us in such a way that we always fail in our attempts to know the truth. Thus, the logical thing would be that we can, to some extent, understand the corporeal world. Descartes called this reality res extensa. He was referring to everything that has an extension and that can be observed, measured, or weighed.

If this is the case, why are we sometimes deceived by our senses? Why do we fail to know the truth? Descartes argued that, when our will to know is greater than our understanding, then we make mistakes. When we want to know something, but we don’t have enough clarity and distinction about it, we’re prone to be misled by false conclusions.

Is Descartes’ argument infallible?

Although some of Descartes’ concepts help us to reflect, there are weaknesses in some of his arguments. We can’t doubt his ideas if we believe we exist but is this enough to affirm that there’s a thinking substance? Some philosophers like Hume maintain that the idea of the self is an illusion and that our existence is a flow of events that don’t conform to any unit.

On the other hand, the demonstration of the existence of God has been strongly criticized. The fact that the ideas of infinity and perfection are possessed within ourselves doesn’t necessarily prove the existence of perfect and infinite beings. Indeed, many maintain that there’s not enough clarity and distinction to consider that these ideas are innate. In addition, we could easily deduce them through negation, contrasting them with the ideas of finiteness and imperfection.

However, despite the criticisms of Descartes’ thoughts, it’s impossible to deny that his ideas had a great impact on later philosophy. Moreover, methodical doubt can be a tool that helps us challenge our beliefs and perspectives and help us expand our knowledge and understanding of the world.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Descartes, R. (1999). Meditaciones metafísicas – Las pasiones del alma, Ediciones Folio, Villatuerta.
  • Pereira Gandarillas, F. (2014). Hume y la ficcion de la identidad personal. Ideas y valores  63 (154), 191-213.

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