I've been reading about internalism and externalism and their responses to scepticism. I'm aware that many regard internalism as more susceptible to a sceptical attack than externalism, for example via the sceptical argument that we lack direct access to facts about the external world. I won't go into details about the argument but have read that many externalists claim lack of direct access doesn't preclude non-inferential knowledge and so take this as a strength of externalism over internalism, because to an internalist assuming a lack of direct access to a fact and a lack of non-inferential knowledge would imply that we lack knowledge. (Please correct me if I have misunderstood the argument).

I have read the Meditations and am trying to understand more about the nature of internalism in Descartes' case. I was wondering how said weakness affects Descartes' internalism, as it seems that he holds justification only comes in the form of ideas and this would be susceptible to the sceptical argument above. At the end of Meditation VI he asserts that he can know he's not dreaming because when he's dreaming he cannot remember past experiences - but as Hobbes noted, he could dream that he's remembering them. This seems like it could apply to many forms of internalism in that it's a weakness for justification of knowledge. I wanted to know: what other possible sceptical attacks could be made against Descartes' particular form of internalism? thank you

  • Idealism in and of itself is hard to counter. But Cartesian Dualism (pluralism) has quite a few vulnerabilities (see Princess Elizabeth of Bohemia)
    – Richard
    Jan 22, 2019 at 20:01
  • I'm not sure Descartes endorsed internalism. He notes that we can always doubt the external world but didn't argue that there isn't one,. .
    – user20253
    Jan 24, 2019 at 11:45

3 Answers 3


Descartes' most famous work, The Meditations, is perhaps best understood as an attempt to seriously consider a radically skeptical argument, and counter it. Whether or not he succeeded has been a debate since the very beginning. It may be worth you consulting the primary source in this case --the Meditations are brief, engaging, and written relatively clearly, without a lot of philosophical jargon.

The core of his argument is this (paraphrased --not a quote):

We can doubt everything else, but we cannot doubt our own existence as a thinking entity, because the very fact of our doubt implies something that thinks is doubting.

Most people agree with that statement, it's his subsequent chain of inferences that people find shaky. If you are interested in some of the chief objections to his arguments, a number of the most famous ones were solicited by Descartes himself before he even published his work. These can be found under the title Objections and Replies to the Meditations.

  • thank you for your answer - I'm sorry, my question was very unclear so I will rephrase it - too long to comment.
    – ashalrik
    Jan 23, 2019 at 1:17

Skepticism is prime mover of philosophy

Essence of skepticism, to doubt everything, not only sensory perceptions but also thoughts and even existence of truth, is what makes philosophy worth of existing. Every philosophical school and every system created by individual philosopher, is susceptible to attacks from skeptics, this is precisely the reason we have so many of them, often mutually exclusive. Response to skepticism is basically two-fold, one is to ignore it, other is to tear down everything and build philosophical system from ground up.

As an example of first behavior, we could take Marxism and its reliance on materialism. Marxism bases itself on (unproven) belief in matter and material universe, and also in belief that we as humans could reasonably accurately investigate this material universe directly with our senses and indirectly with our instruments. Marxists refused the debate this with the skeptics, proclaiming such debates as unfruitful . Skeptics on the other hand refused to recognize Marxisms as philosophical system, and declared it to be more of dogma, almost religious, and as such dogma it would inevitable fail sooner or latter (which in the end did happen).

Other approach is approach taken by René Descartes. Fact that we even today still debate about his work shows its quality. Meditations on First Philosophy has six chapters, but only first two are usually cited and largely accepted among philosophers. Other four were attacked and arguably successfully refuted centuries ago. These four latter chapters largely concern the existence of God and are trying to prove that a) God must exist b) that God must be perfect (not a Evil demon deceiver). In his time Descartes was under a threat of being declared heretic, and that could be a part of his motivations to try to "prove" existence of omnipotent, benevolent God. It must be said that his arguments in this case are much weaker then for example his arguments concerning Cogito, ergo sum in chapter 2.

What we could say today about Meditations ? Book has six chapters, first is based on almost pure skepticism, last four are not very relevant, but at least chapter 2 stands as shinning example of philosophy, required reading for anyone even slightly interested in it. Is the work of Descartes vulnerable to skepticism ? Yes, but that is how it supposed to be. That even parts of it survive and are universally accepted today is a miracle. Compare this to the numerous philosophical systems left to oblivion and you will understand its worth.


** I'm aware that many regard internalism as more susceptible to a sceptical attack than externalism, for example via the sceptical argument that we lack direct access to facts about the external world.**

Externalism does not require that we have direct access to facts - events or states of affairs - about the external world. Its distinctive requirement is that there should be a reliable causal connection between the external world and our beliefs or other states of mind. If the 'right' connection, or kind of connection, holds regardless of whether we have any notion of what it is or whether it holds, then our beliefs are correct. Our beliefs simply need a certain origin.

It is perfectly possible for a deviant causal chain to connect a belief to its origin - a causal chain that purely accidentally causes a correct belief. Such a belief would be open to 'sceptical attack' because it is epistemically sub-standard and unreliable. (It would fail the test of reliabilism.)

I can't see that internalism, Descartes' (if he was an internalist) or anybody else's, is any more exposed to 'sceptical attack' than externalism. Unless direct or 'naive' realism is true, the internalist 'lacks direct access to facts about the external world' but so does the externalist. If the internalist is always at risk of judging on the basis of inadequate or otherwise faulty evidence and of making false inferences, so is the externalist in tracking the causal origin of our beliefs or other states of mind.


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