For Descartes, is madness fundamentally different to dreaming?

Reading these blog posts (I am unfamiliar with the discussion really), which has a few points against Foucault's analysis that it is fundamentally different to dreaming.

“Descartes replies by quoting the case of dreams which produce eccentricities as great as those of madness, but to which we are all, each one of us, exposed,” Foucault correctly summarizes Derrida's argument.

Foucault responds first absurdly, suggesting that somehow this objection proves Foucault's own point. It does not, and Foucault makes no argument to suggest that it does.

For Foucault, Descartes claims madness is not the same as dreaming because not all of us can claim we may be mad, we are not all mad (perhaps shorn up with the dis-analogy that mad people interact with actual other people, unlike dreamers).

Was Descartes rhetorically claiming not to be mad?

Descartes.. may doubt his senses, he may doubt his body, but he never takes up madness as his own subjective position

Claims Foucault. Derrida replied

Descartes [says]... since I am here, writing, and you understand me, I am not mad, nor are you, and we are all sane... he feigns to rest in this natural comfort.. to unsettle himself from it and to discomfort his interlocutor.

The blog claims that Derrida conclusively disproves that

Descartes considered mad hallucinations about having a pumpkin for a head as something separate, something fundamentally different, from the dreamer's hallucinations that he is not asleep in his bed but sitting his drawing room... this absurd position about madness

But that conclusion only works, I think, if Descartes was not really - only rhetorically - rejecting madness and saying he wasn't mad (unless he did successfully account for all knowledge, not just his own, which would be a very "totalitarian" claim).

“Philosophy presents itself as the universal criticism of all knowledge (the first postulate), without any real analysis of the content or the forms of this knowledge,” Foucault says [in claiming that it is totalitarian]... [but in fact] Descartes' meditation... is nothing but an analysis of the form knowledge takes.

For what it's worth, I don't think dreaming is analogous to madness here, that while mad people may - as much as anyone - know with certainty they exist, if I am mad then someone else is sane, unlike dreaming, and this changes the nature of doubt, whether or not a mad person could have written Descartes' meditations.

  • even if Descartes' argument would work just the same for madness as dreaming, that doesn't mean they are "fundamentally" the same or that Descartes does not treat them differently. what a strange blog post
    – user67302
    Commented Aug 18, 2023 at 1:28
  • I just want to say that the phrasing "For Descartes, X..." or "Foucault's Descartes..." is fundamentally irritating to me. The language suggests that all of Descartes' claims are "true for Descartes" regardless of their actual truth, or that Foucault could have "his own Descartes" about which he could make any statement he liked and it would be true for Foucault.
    – causative
    Commented Aug 18, 2023 at 2:58
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    I don't see that F implies D is not mad. F is suggesting that D's conjecture and conclusions are marred by his (D's) non consideration of the possibility What if I am mad?
    – Rushi
    Commented Aug 18, 2023 at 5:08
  • Also related: Spinoza accused Descartes of insincerity even he concluded his being from 'cogito ergo sum'. The question here is same or analogous
    – Rushi
    Commented Aug 18, 2023 at 15:34
  • i may have phrased it wrong @Rushi
    – user67302
    Commented Aug 18, 2023 at 20:14

1 Answer 1


Descartes, Derrida, and Foucault were not mad (that is, insane in modern terminology). In addition, none of them had or have any grasp of neurophysiology and none of them were or are trained behavioral health clinicians.

This means any assertions made by them involving "madness" are not informed by personal experience, professional experience, or training, and may therefore be dismissed without argument.

  • 2
    I'm not trained as an auto mechanic so anything I say about cars can be dismissed. This explains a lot...
    – Scott Rowe
    Commented Aug 18, 2023 at 10:26
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    I'm not a Foucault fan, but i have to coment on this. When he tries to discuss the nature of madness or even the criterias that society uses to classify madness, one does not need to be a physician, because hes reasearch is exactly about the presupositions that physicians make to say someone is insane. First you have to assume that you are plenty capable to define without a doubt this terms, second, one has to be certain this fenomena exists in the first place and is not a mere convention. This is the Foucotian discussion.
    – LAU
    Commented Aug 30, 2023 at 1:31

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