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Cogito, Ergo Sum: René Descartes’ Grand Idea

René Descartes’ cogito, ergo sum is one of the most famous pronouncements in the history of philosophy. It has also been blamed for subject-object distinction in Western philosophy and the dualistic view that has dominated the way that academics speak about the mind. Dr. Orton explores the debate.

 

For A Level Philosophy and Religious Studies students, this is an overview of one of the most important topics you will need for your exams. For university-level scholars or independent researchers, we’ve included clickable links to useful literature and canonical scholarship you need to be acquainted with to get started.


René Descartes

 

My PhD and undergraduate degrees were completed partly in the discipline of Philosophy, so I have long been aware of René Descartes’ importance. What I hadn’t anticipated was how significant his ideas would be in Anthropology, Folklore and Religious studies, which I came to later in my career.

 

I began hearing at Folklore conferences that “We are all children of Descartes”; at Religious Studies conferences, I would hear, “Descartes created the subject-object distinction: we all have to unlearn that.” What did people mean?

 

Arriving at the Cogito

 

Few statements in the history of Philosophy have had such an impact as that of cogito, ergo sum by René Descartes – least of all those made in Latin. Yet, the pronouncement is almost as familiar to the lay person as it is to the scholar. What did Descartes mean by it?

 

Descartes was interested in the epistemological question of how we can know anything at all. He produced sceptical arguments known as the three waves of doubt: firstly, he doubts the reliability of his sense experience – is he suffering from an illusion? Secondly, he asks whether he might be dreaming. Finally, he suggests that he might be deceived: an evil demon may be controlling his experience, even to the extent of making him think that he is adding up correctly.

 

Descartes arrives at the conclusion that there is one thing he can know for sure: that he is thinking. As he is thinking, Descartes himself must exist: cogito, ergo sum (“I think, therefore I am”).

 

Descartes’ cogito as an example of an a priori intuition. Intuition is when the rational mind apprehends the truth or falsity of something with immediacy, without any process of reasoning or inference.

 

Descartes points out that we cannot doubt our own existence since that presupposes that we exist in order to do the doubting. We can therefore see that our existence is a clear and distinct idea, intuited a priori.

 

Descartes’ notion of “clear and distinct ideas” is that some ideas can be perceived as we would perceive something visual clearly with our eye. An idea is distinct when it is so sharply separated from all other ideas that every part of it is clear. Descartes claims that since the Cogito is a clear and distinct idea which he knows to be true, then clarity and distinctness must ‘as a general rule’ be a sign of truth.

 

Descartes’ Philosophy of Mind

 

The mind-body problem in Philosophy of Mind is that humans have (or seem to have) both physical properties and mental properties. Materialists say that, despite appearances to the contrary, mental states are just physical states, whereas idealists say that physical states are really mental. Dualist views say that the mental and the physical are both real and neither can be assimilated to the other.

 

Descartes held a view of substance dualism, meaning that the mental and the physical are both real, cannot be reduced to each other and are composed of different substances. Whereas the body is physical, the mind is a non-physical substance.

 

Descartes’ use of the cogito forms part of the conceivability argument for substance dualism. Because “cogito, ergo sum” is known only from the fact that it is “clearly and distinctly” perceived by the intellect). Descartes argues that, because we are able to ‘clearly and distinctly’ conceive of two things being separated, they must logically be separable.


Antoine Arnauld

 

Descartes’ also makes the indivisibility argument for substance dualism, claiming that it is always the same, indivisible self that experiences the world; it appears impossible to be conscious in two places at once. This is not possible for the body (or even the brain). Using Leibniz’s Law (if two things share the same properties, they are the same thing; if not they are distinct), Descartes argues that minds are distinct from bodies. 

 

In fact, though, Descartes has only established that there is a thinker - it may not be him.

 

David Hume objected on empiricist grounds that mind without body is not conceivable. Hume was an empiricist, arguing that we can only derive knowledge from experience.

 

Hume points out that we have a series of conscious experiences, but we do not have experiences of a single thing that has these experiences. Whenever we try to introspect and experience this ‘self’ we believe in, we only ever experience ourselves as a “bundle” of ever-changing mental states.


Hume says, “For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I can never catch myself at any time without a perception, and can never observe anything but the perception. When my perceptions are remov’d for any time, as by sound sleep; so long am I insensible of myself, and may truly be said not to exist.”

 

Other objections include Antoine Arnauld’s point that what is conceivable may not be metaphysically possible (using the example of mathematical entities). Moreover, what is metaphysically possible tells us nothing about the actual world.

 

The masked man fallacy shows that intentional states, like belief, hope and desire do not follow Leibniz’s Law. Consider: (i) My idea of Batman is of a masked crusader (ii) My idea of Bruce Wayne is not a masked crusader (iii) Therefore, Batman is not Bruce Wayne.

 

Additionally, the mental is divisible in some sense: when the corpus callosum (which links the left and right hemisphere of the brain) is severed, some patients seem to experience a "split brain" or "divided mind." 

 

Also, there is no necessary link between being indivisible and being non-physical; conversely, not everything thought of as physical is divisible (running, for instance). However, we do not say that this must mean it is a different substance.

 

Gilbert Ryle makes the additional argument that Descartes’ concept of the soul is “the ghost in the machine.” Ryle argues that Descartes commits a category error by assuming that events must be either mental or physical. If someone were to attend a cricket match hoping to see “team spirit,” they would come away disappointed if they expected that team spirit was a separate entity to the players, equipment and other components of the match.

 

Perhaps one of the most historically significant objections to Descartes’ substance dualism comes from Elisabeth, Princess Palatine of Bohemia, with whom Descartes shared a long-standing correspondence discussing the problems of philosophy. Elisabeth’s letters point out that Descartes’ theory that there are two distinct substances of mind and body would create significant difficulties in explaining how they interact with each other causally and the nature of their union.


Elisabeth, Princess Palatine of Bohemia

 

Descartes and Deduction

 

Descartes used the approach that gave him the cogito to prove other ideas about the world. His arguments for the existence of God and his proof of the external world are examples of a priori deductions.

 

Deduction is using premises to reach a conclusion the truth of which is entailed by the truth of the premises. If we can know that the premises are true and that the conclusion follows deductively from them, we can know the truth of the conclusion. 

 

In the Meditations, Descartes reasons that (i) he has a clear and distinct idea of a physical substance and (ii) his perceptions are involuntary and thus cannot come from my own mind. Therefore, either physical objects or God must cause his perceptions. He further reasons that (iii) the source of these perceptions cannot be God as God is not a deceiver and (iv) (according to other arguments of Descartes) God exists. Therefore, the source of my perceptions must be physical objects, and therefore, an external world exists.

 

Aside from the philosophical issues with each of Descartes’ individual claims, his deductive method is challenged on empiricist grounds by David Hume in “Hume’s fork.” Hume claims that all objects of human reason or inquiry are either relations of ideas or matters of fact.


A priori reasoning can only tell us about the relations between ideas, i.e. analytic knowledge (true by definition). An example of this is, “a bachelor is an unmarried man.” A posteriori reasoning can only tell us about matters of fact, i.e. synthetic knowledge (true in virtue of the way the world is). An example is, “alligators live in Florida”.


David Hume


Analytic truths are different from synthetic truths and arrived at by different types of reasoning. Hume’s problem is that Descartes’ use of intuition and deduction uses a priori reasoning yet comes to a conclusion about matters of fact regarding the existence of an external world.

 

Descartes’ Influence

 

From speaking with other scholars, my sense is that Descartes has shaped Western thought with two related claims: that the human mind is a non-physical substance that is separable from the physical body and, consequently, that there is a subject-object distinction. The subject is a thing that thinks but has no physical extension and the object has physical extension, but does not think.

 

If it is right that Descartes’ influence has been so dominant, these ideas would indeed shape the way we approach other societies who have not been subject to it - and the way we think about ourselves.

 

My sense is that Descartes’ ideas have been enormously important – but they have not gone unchallenged, as we’ve seen here. Could his influence on the way anthropologists, religious studies scholars and folklorists have considered other societies have been overstated? Read more about the debate in my next post on personhood and the self in Western and non-Western societies!

 

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