Is there a flaw in Descartes' "clear and distinct" argument regarding the separation of mind and body? I think that there is a flaw in the argument. I got this idea from an online lecture. Here is my own version of it.

For two things to be separate it is not sufficient that one thing can be perceived clearly and distinctly from the other. What must be done is to establish that one thing can be perceived without the existence of the other and vice versa. However there is a problem. Doesn't this procedure sound quite extreme? I cannot clearly perceive myself forgetting about my body nor can I perceive my body forgetting about myself. But can I really not perceive myself without the existence of my body? How can I ever know is the immediate question. And the immediate implication is that I cannot perceive myself without (or forgetting about) my body. Otherwise there wouldn't be the immediate question "how can I ever know?".

Now if this argument is correct then what Descartes has paved the way for is proving the unity of myself and my body. What then? Is the problem really solved?

  • The argument is analyzed in IEP's Real Distinction Argument. Their conclusion about its main flaw is this:"In the end, the main difficulty with Descartes’ real distinction argument is that he has not adequately eliminated the possibility of minds being extended things like brains."
    – Conifold
    May 16, 2017 at 20:13
  • 1
    Hi. Descartes's argument does not require that you forget your body. It is enough that what you think of as your body might be an illusion, as it is in dreams. May 16, 2017 at 22:20

5 Answers 5


"Is there a flaw in Descartes' "clear and distinct" argument regarding the separation of mind and body?"

Descartes was well aware of the difficulty, and what actually says is that although mind and body seem distinct they also seem to form a unity. I feel he is unfairly accused of setting mind-body dualism in stone since he recognised the need to unify them.

I'd agree with your argument up to...

"But can I really not perceive myself without the existence of my body? How can I ever know is the immediate question. And the immediate implication is that I cannot perceive myself without (or forgetting about) my body."

'Perceive' is the wrong word here since it implies physical senses belonging to the body. If you ask whether you can know that you are not your body then according to many people the answer would be yes.

"Now if this argument is correct then what Descartes has paved the way for is proving the unity of myself and my body. What then? Is the problem really solved?"

It isn't solved by just saying that you and your body form a unity. For a full metaphysical solution you would have to expand this unity to include the whole universe, where the world of space-time is the 'body' that must be reduced for unity.


Descartes' views as to the relation between mind and body should be understood on the basis of the two main notions he used of "clear and distinct idea" and "doubt", together with the Cogito, "I think, therefore I am".

We can all decide for ourselves if the Cogito is indeed a clear and distinct idea and if I should be in no doubt that I think. If we accept these premises, however, it follows that the thing which is doing the thinking exists. This thing is referred to in the Cogito by the pronoun "I". Descartes explains at length what is this thing, namely the thoughts themselves. So, according to him, there is no doubt that our thoughts exist, at least whenever we are indeed thinking them. The term "mind", in this context, should be understood as referring only to these thoughts, the thoughts that you have at the moment you have them. In this sense, we know our mind exists. Or, rather, our mind knows it exists. Descartes thinks there is no equivalent certainty as to the existence of our body, and indeed gives many examples for why this is so.

Again, we are all free to accept or reject his conclusion in this respect. The main point here, however, is that all that Descartes' Cogito shows is that there is this clear and distinct epistemological difference between the mind and the body: we definitely know our mind exists but we can only believe our body exists. This is if you like an epistemological Dualism and this is all that the Cogito should be understood as supporting.

Descartes went much further than the Cogito but life goes on after the Cogito and we all have to go beyond the Cogito and make up our minds as to the existence of all sorts of things, but this time we have to do that without the support of a clear and distinct argument like the Cogito.

I may be wrong but I don't expect you will find this interpretation in the vast body of literature on the Cogito.

All the same, as I see it, the Cogito works from the first-person perspective and only from the first-person perspective. Crucially, the Cogito is not a claim about other people's mind. Thus, we can only decide for ourselves whether the Cogito is effective as an argument. At least for now, there would be no point in making a claim about the existence or otherwise of somebody else's mind.

All we may need in relation to the Cogito is to understand how it works. There are two basic aspects: whether the Cogito is a valid implication and whether the premise is true. We can easily all agree on the validity of the implication. However, for now at least, each of us is the only person who knows whether he or she is thinking, and therefore whether the premise "I think" is true or not. This is certainly a serious limitation! On the other hand, we can all make up our own mind about that, assuming we have a mind.

If we don't have a mind, I don't think we need to care about the Cogito.

But if you do have a mind, you probably don't need to care much about what people who may not have one say about the Cogito.

  • I like your answer but do you have references that point me to others who hold similar positions to the one you are presenting? May 14, 2018 at 13:39

I don't have a lot of time right now because of finals, but thought you might like to read Princess Elisabeth of Bohemia's response to Descartes regarding mind-body dualism. Descartes is not arguing for the unity of mind and body. He tries to satisfy Elisabeth with a third substance that is the unity of mind and body, but the rest of his argument relies on that distinction, so his response to her criticism falls short of satisfactory.

I will say that the cogito argument establishes that the mind exists (I think therefore I am) because to reject that you are thinking is itself a contradiction. I, for one, can perceive of my thought as separate from my body. For example, I have dreamt of rising out of my body, and otherwise of being separate from my body. Part of what is being established here is the epistemological distinction between things that are known a priori versus a posteriori, that is, known separate from experience vs. from experience. This mirrors the ontological distinction of analytic vs. synthetic, and until Kant were generally thought of as the same split.

This should at least give you some more things to ponder. Now, back to studying for my ethics final.


Spinoza follow Descartes' "clear and distinct" (or scientific) method up until the question of the pineal gland, as the connecting point. In his Ethics. I believe, however, that your way of conceiving of the problem does not confront Descartes for the reason that he does not think of the matter of a "self" and a "body" in the modern way. Rather, everything, the whole world, is the cognito. And the extended world is a secret, invisible place, where mechanical action, as a Philosophic Material, is supposed as a hypostasis or Reality behind the appearance. So it is not entirely one's fault for not being able to confront Descartes on his own ground, so to say, but his way of thinking is simply bizarre to the modern mind. Reviewing the objections in Spinoza may be a way to get more familiarity with the issue. Though, it is largely unimportant for the modern mind body question, or something of that kind.

  • Unimportant for modern mind-body question? It seems utterly crucial to me.
    – user20253
    Aug 17, 2017 at 11:12

Decartes methods and theories were brilliant for their time. However, the assertions of a separate and detached possession we each have, which he claims is the invisible mind, has always been a major flaw in his reasoning.

Daniel Dennett extrapolated the modern Cartesian model into what he calls, “Cartesian Theater’. Represented as a series of viewers, each interpreting the same instance of the singular subject viewer and providing evaluations of the same.

If you take Decartes’ Methodology of mind as a skill set with which to learn and observe the world you are immersed in daily, it becomes a technology.

The division of a referential self into a dualistic entity interferes with our clarity of thinking. A subjectively defined Cartesian ‘invisible self /mind’ model has been allowed to intrude on our thinking, causing many errors to how we perceive our identity. We are linguistically trained to falsely identify it as part of who we are. The Cartesian dualistic model of self is less disciplined in deliberate thought processes. It is best used as a modified technology we are able to apply to learning and investigative research.

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