Can one doubt their own existence in the world while simultaneously doubting the existence of others? If one's being isn't present because they aren't present themselves, wouldn't that make it illogical to doubt other people ontological presence or existence because your influence on others is already within the pool of doubt?, according to Cartesian philosophy?

For instance, would it be logical, from a Cartesian perspective, for someone (let's call him A) to doubt his own existence while also doubting the ontological presence of others in the world?

  1. "A" doubts his existence.
  2. "A" questions existence as existence.
  3. "A" doubts whether the person he interacted with has ontological presence, whether it's true or not.

But wouldn't propositions 1 and 2 oppose proposition 3? If "A" doubts his own existence, it implies doubt in existence itself, making it logically challenging for him to doubt the ontological presence of others. Descartes introduced a skeptical method called methodological doubt or metaphysical skepticism, leading to the undeniable fallibilistic insecurity of our knowledge and the world around us.

If "A" is epistemically insecure about his existence, then he must also be epistemically insecure about his surroundings. His phenomenological perception becomes irrelevant, as doubting himself implies doubting the surrounding. Wittgenstein argued that qualia are limited within a peripheral "place," meaning phenomenological consciousness can't experience beyond its own limits. Wittgenstein used conceptualistic, intentional, and semantic inferences, as well as the pragmatic use of language, to explain this limitation.

So, from a Cartesian perspective:

  1. Would it be logical for someone to doubt their existence and then doubt the ontological presence of others?
  2. If "A" already doubts himself, wouldn't he be limited phenomenologically, contradicting Wittgenstein's postulate? How could he doubt others' existence while having such limitations?
  3. Did Descartes ever provide an explanation for this, and how does it make sense from a Cartesian viewpoint? And how would he respond?
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    I think the premise of this question is flawed. It is logically impossible to doubt one's own existence--that is the point of the Descartes' cogito. I guess you're right that if you doubted your own existence it may make doubts about others' existence meaningless. But that doesn't apply to the Cartesian framework, for the reason mentioned above. I don't have any idea what you're attributing to Wittgenstein, so it may help to provide some sources there. Commented Apr 13 at 18:17
  • @transitionsynthesis: But Descartes begins by doubting even that, before identifying the cogito. Cartesian Method is methodological scepticism, where you doubt things & then find counter arguments to those doubts.
    – CriglCragl
    Commented Apr 13 at 19:26
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    @CriglCragl That's simply not accurate. Read closer. At the end of Meditation 1, Descartes doubts the existence of the "body, shape, extension, movement and place". It is only at the beginning of Meditation 2 when it occurs to him to apply the doubt to his own existence. Immediately upon attempting to doubt his own existence, he discovers he cannot. The cogito is not a dialectical counterargument to skepticism, it is a direct intuition of his own existence to which he is led by the skeptical device (as Descartes says in his reply to the objections which you can find in the Cambridge ed). Commented Apr 15 at 20:54

1 Answer 1


Of course you can. Scientific Method involves only holding truths to be as sure as the evidence we have. And to remain open to new evidence, that may change the balance of evidence. Your doubts may be small, but as a scientist certainty is impossible.

Simulation Theory, and Boltzman Brains, are ideas which (depending how you define terms) could make both self and others not meaningfully real, or not exist in the way we feel they do. You can use Occam's razor or whatever, but a scientific perspective just says, what evidence do we have for what? I mean, self and others don't even exist in physics, except as conceptual shorthand for certain lumps of chemistry: we are all just dissipative phenomena in the story of one universe, and it's journey from a currently inexplicable compact low entropy state towards darkness silence and cold. Self and other are as meaningful only as 'droplet' or 'pile'.

You can doubt yourself in layers, indeed this is a main issue with Descartes. What is the the 'I' of the cogito? Does the cogito really reveal anything about it? We have conceptual tools now for considering the self in different contexts, which he didn't have. Is the subconscious or unconscious part of the self? What if you upload the mind, or multiply it by teletransportation? Do we not exist under anaesthesia? What about under dissociative drugs that suppress the default-mode-network? All Descartes gets at is that there is some kind of algorithm happening which means there must be a subjectivity, because that is implied by the definition of thinking. But where did those terms and concepts come from? Not the individual mind itself, but from language, which requires having been in community, and learning them through language-games and shared-modes-of-life.

You can't really logically dismiss solipsism out of hand. But you can look to evidence, and you can look to pragmatics. It's like free will, which even vigorous sceptics of say we need to act like it's real for individuals and society to function.

I see self and other as real like the concept of fiat-currency makes money real: it is our lived enactment of it being real, which is it's reality. We use the terms consistently and coherently, we live the modes of life that express them.

"In this sort of predicament, always ask yourself: How did we learn the meaning of this word ("good", for instance)? From what sort of examples? In what language-games? Then it will be easier for you to see that the word must have a family of meanings."

-Wittgenstein, in Philosophical Investigations

Intersubjectivity, allows us to dispense with the confusions generated by assuming we can access transcendental objectivity.

You can doubt whatever you like. The question is, can you make it useful to have done so? The intersubjective perspective shows us that we should take seriously the idea of a peer-to-peer ontology (at least of things beyond the layer of qualia), like in the ancient metaphor of Indra's Net. Accepting that can shew the fly out of many bottles.

  • @Muhhamedbinghazi: Applying scepticism doesn't mean you can't say 'If this is true, this other thing follows'. Maybe it would help to consider an example: an ancestor simulation being run to test the full range of an individuals choices, while keeping everything else the same - the self would not be fixed or real in the conventional sense, it would be a variable, while all the other people would be simulations of people the indivudual originally interacted with, but able to respond to the changes. Computer games are typically like this, respawning the protagonist until some goal is achieved
    – CriglCragl
    Commented Apr 13 at 21:00

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