Foundationalism and distinct. Geometrical truths are also certain and indubitable; Descartes thus attempted to find truths which were clear and distinct because they would be indubitably true and a suitable foundation for knowledge. His method was to question all of his beliefs until he reached something clear and distinct that was indubitably true. The result was his "cogito ergo sum" – 'I think therefore I am', or the belief that he was thinking – as his indubitable belief suitable as a foundation for knowledge. This resolved Descartes' problem of the Evil Demon – the possibility that he was being deceived by
Cogito, ergo sum exists, then I exist"). In "Descartes, The Project of Pure Enquiry", Bernard Williams provides a history and full evaluation of this issue. Apparently, the first scholar who raised the "I" problem was Pierre Gassendi. He "points out that recognition that one has a set of thoughts does not imply that one is a particular thinker or another. Were we to move from the observation that there is thinking occurring to the attribution of this thinking to a particular agent, we would simply assume what we set out to prove, namely, that there exists a particular person endowed with the capacity