Descartes Contra Wittgenstein
“It may easily look as if every doubt merely revealed an existing gap in the foundations; so that secure understanding is only possible if we first doubt everything that can be doubted, and then removed all these doubts.” --Ludwig Wittgenstein , Philosophical Investigations , section 87 I. I think, therefore I am Descartes' famous principle, cogito ergo sum ("I think, therefore I am," also known simply as the cogito ), is probably the most widely known philosophical statement, and it is often considered to exemplify the only thing one can know for certain: that one exists. The cogito might be considered an instance of modus ponens : "If I am thinking, then I exist; I am thinking, therefore I exist." However, Jaako Hintikka ( 1962 ) compellingly argues that Descartes' cogito ergo sum is not a logical inference at all, but a performative act: that a certain cognitive act instantiates direct knowledge of one's existence--that the act of thinking make...