In the Philosophy Now piece, 'Heidegger's Ways of Being', Andrew Royle claims that Martin Heidegger offered us a “direct refutation of Rene Descartes' solitary introspection”. Is that really the case?
Descartes “global scepticism” was an epistemological exercise. It had little - or nothing - to do with ontology. It was about how Descartes – or about how we - could know, and then philosophically demonstrate, that (to use Andrew Royle's own words) “the world and other people actually exist”. It wasn't even that Descartes didn't believe that the world and other people existed. Descartes' enterprise was about his knowledge of other people's existence. Indeed Descartes' initial scepticism is also what's called “methodological scepticism” (or “methodological doubt”). That is, it was supposed to be sure route to knowledge. It was a philosophical method which was designed to show us that knowledge of the world and other people is possible.
As for the Heideggerian grammar of the word 'I'.
Say, for argument's sake, that the use of the word 'I' also (as Royle puts it) “necessarily refers to... 'you' or an 'other'”. How did Descartes know that all the people he'd experienced weren't also the simulations of an “evil demon”? Thus such simulations (or mental distortions) might have also grounded Descartes' use of the word 'I'.
To put that another way. If the Matrix and “brain-in-a-vat” (Hilary Putnam) scenarios are possible, then it's equally possible that the simulations we have of other people may ground our use of the word 'I'. Indeed one can even say that a Heideggerian notion of “social Being” (or Dasein) can exist alongside Cartesian scepticism – indeed even if the Matrix and brain-in-a-vat scenarios are possible. (Putnam, of course, argues that his own scenario isn't possible – and for loosely Heideggerian reasons!)
As for solipsism. To quote Arthur Royle himself:
“Although Heidegger's argument works to abate Descartes' solipsism... Whilst the 'I' (or 'ego') was indubitably alone for Descartes...”
In everyday-life terms, Descartes would have left his doubts well behind after he'd solved (or thought he'd solved) the “sceptical problem”. (Just as Hume forgot his own scepticism when playing billiards.)
This means that Descartes most certainly wasn't a solipsist. (Though it can of course be said that he was a “methodological solipsist” for the duration of the Cogito.)
A genuine solipsist is someone who does indeed have an ontological position on what Royle calls the “I” or “ego”. What's more, a solipsist feels the reality of his solipsism throughout his life. (Or at least he does so for as long as he's a solipsist or thinks about his philosophical predicament.) Descartes, on the other hand, took a journey from his radical scepticism to a sure knowledge (or so he believed) of the world and other people. Now that's very far from being solipsism.
Not only that: solipsism has ontological and ethical implications. However, that isn't really the case when it comes to Descartes' scepticism. Having said that, it's indeed the case that certain political and sociological theorists have interpreted Descartes' scepticism as a 17th-century philosophical expression of “bourgeois individualism”. Yet even if that were true, Descartes never made this explicit. With Heidegger and solipsists, on the other hand, their ontological and ethical positions are indeed made explicit.
Paul Austin Murphy.