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