As we all know, Kant wrestled with Cartesian skepticism for a long time. And of course, Descartes himself did, but he appeals to a version of the ontological argument which is not very persuasive.

What other philosophers tried to give a serious refutation of skepticism about the external world that in some way goes beyond an appeal to common-sense (which at a first glance is the basis for George Edward Moore’s “here is one hand”-argument)?

  • Radical skepticism is acknowledged to be irrefutable, a sufficiently determined skeptic can deny any premise used to "refute" him. The arguments (including Moore's) are rebuttals to the skeptical arguments. Dretske noticed a common closure pattern used in them:"if you know that this is a chair then you know that you are not dreaming/hallucinating/deceived, you can not know that, ergo" and argued that the closure is invalid, see Epistemic Operators. General approach in formal epistemology is to isolate the epistemic assumptions that skeptics require.
    – Conifold
    Commented Aug 29, 2019 at 20:23
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    @Conifold imho the Cartesian skeptic is seductively convincing because he manages to drive a wedge between the objective and the subjective world. Especially since with the cogito he can present something “irrefutable” – with virtually no disagreement. He isn’t just a skeptic naysayer, he gives a standard that he expects proponents of the external world to meet.
    – viuser
    Commented Aug 29, 2019 at 20:46
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    @PeterJ So we should all accept that it is possible that a conscious being is manipulable up to the level of making their whole life an illusion. It sounds like a joke to me, a very dangerous one.
    – user34482
    Commented Aug 31, 2019 at 13:37
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    This is just a side note, but Descartes can't really be said to have "wrestled with Cartesian skepticism". Descartes was never worried about refuting skeptical hypotheses. "Skepticism" there is not a threat, not an opposing position, but a tool, a method. And the method is purgative: the Meditations are meant to help the individual expose and rid himself of his habit of relying on sense-perception and imagination as a source of knowledge. The meditator knowingly and willingly enters into the suspension and makes use of the method and puts the method down when he is done meditating for that day Commented Aug 31, 2019 at 20:15
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    @RiccardoAquilanti - It's not a joke, it's the Perennial philosophy. No manipulation is required. There would be a sense in which life is an illusion but it might be less misleading to say it is not what we think it is. Scepticism in Western thought is a dead-end that looks like the end of philosophy but this is only because it rejects the form of scepticism endorsed by mysticism. This is an optimistic doctrine that explains why we cannot falsify solipsism.or prove naive realism. To argue for naive realism is to argue against this doctrine.
    – user20253
    Commented Sep 5, 2019 at 12:56

3 Answers 3


Daniel Wildcat, a Native American philosopher has written in a discussion of indigenous metaphysics:

Teaching American Indians and Alaskan Native students Descartes Meditations on First Philosophy and Discourse on Method of Rightly Conducting Reason and Reaching the Truth in the Sciences is difficult because the problem he poses is foreign to the general metaphysical foundations of indigenous North American worldviews.

To doubt one's own existence seems not only unreasonable but suggestive of serious illness within indigenous worldviews. The famous 'I think therefore I am' is an ex post facto truism not only at the level of logic, but also of experience too. That Descartes found it necessary to logically prove something that could be accepted by virtue of experience only indicates the extent to which experience in the world became increasingly problematical for the Western psyche.

What appears then, to be simply common sense, is much more than simple, and actually deeply complex and sophisticated.

  • Thank you for locating a source which exposes the psychological immaturity of the person who denies what is impossible to deny, that humans are born with an intuitive understanding of the ability humans are born with. Spinoza voiced the same message in a more pointed manner, essentially accusing Descartes of hypocrisy. Yes, t. s. it was an attempt to overcome relying on imagination, but nevertheless it was completely avoidable and has left generations of people in doubt about their own ability to understand the truth. CMS
    – user37981
    Commented Jun 4, 2020 at 12:37
  • @CharlesmSaunders Would greatly appreciate the Spinoza reference for «Descartes is hypocrit(ical)»
    – Rushi
    Commented Jun 5, 2020 at 3:30
  • @Rusi-packing-up, Ethics Part 3 page 1, paragraph 2. it begins; "The Illustrious Descartes... There are other mentions of how Spinoza was disappointed that a person of Descartes capability stopped short of the logical conclusions to his statements on substances [Des. definition thereof] and attributed 'cause' to the pituitary gland. CMS
    – user37981
    Commented Jun 5, 2020 at 12:50
  • @charles thanks — appreciated! But I don't quite see what you are alluding to (above)
    – Rushi
    Commented Jun 5, 2020 at 13:12
  • Spinoza's mentions of Descartes are scattered throughout the text. My hope is that this one example will suffice to encourage anyone interested to read through. Reading the 'Ethics' is always time well spent, cheers.
    – user37981
    Commented Jun 6, 2020 at 8:29

If you are the only being in the world, then what makes your life hard? It is quite reasonable for there to be another part of yourself that hates you. But then, what is the distinction between that other part of yourself and another being? If there is just more of you, at odds with itself, how do you consider yourself to be a single being with a single agenda. But if you are a single being with multiple agenda, then what does that mean?

Ken Wilber, a trans-Jungian theorist who integrates Eastern and Western philosophical traditions into an "integrationist" therapeutic model, points out that these distinctions between single and multiple beings, single and multiple agenda are each sometimes true and sometimes false.

At different levels of aggregation and abstraction, we are all one organism, or we are different species of organisms, or we are different societies of organisms, or we are different families of organisms, or we are simply different individual organisms, or we are a body and a mind, or we are multiple minds despite our identified physical boundary, or we are multiple minds working across multiple identifiable physical boundaries, or... Identity, and with it various related processes of homeostasis, goes all the way up at least to the planet, and all the way down to the folded proteins that power the multiple different kinds of organelles within each cell.

Daniel Dennett is a bit obsessed with the notion that the separate cells of your body were evolved to survive independently and to compete with one another, but they are bound together against their potentially divergent wills to participate in your overall conscious process. This is parallel to the way microbiology points out that the organelles that exist in our cytoplasm, which make individual cells work, like mitochondria and Golgi bodies, originate as separate prokaryotic species with very divergent agendas, and are enslaved in a way by the nucleus as a resident overlord.

So it seems silly to answer the question. It can only limit our insight. And it is almost certain to be wrong at least some of the time. If this is all me, it is still all here, in competition and collaboration with itself. If it is not all me, there is a greater me of which it is all part, but there are also sources of agenda outside me. Identifying with different layers of it is productive at different times. That makes what is 'external' a matter of circumstance, and renders this a meaningless question.


You may have a look at Sartre's : A fundamental idea of Husserl's Phenomenology : intentionnality.

( Also, interesting comments on Sartre at Paul Vincent Spade's personal site)

  • Skepticism regarding the external world derives from a false interpretation of the cartesian "cogito" according to which the Self is , so to say, a prisoner of his own mind or of his own thoughts.

  • What the cartesian effort to doubt everything reveals, in fact, is that it is impossible for me to doubt the presence of the world, the phenomenon of the world is a necessary aspect of consciousness itself: " every thought, every consciousness is consciousness of something".

  • The false picture is : (1) there are first two things, two " substances" independant from one another , the Self on one side , the World on the other side (2) how to connect these two substances, how is one substance going to enter in relation with the other?

  • The true picture is : there is an internal ( necessary, essential) relation between the self and the world; the relation is what makes possible both the self and the world.

  • The " being external" of the world is constituted in the " inside" of consciousness itself.

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