Cartesian doubt is the basis for Descartes' statement, ""Cogito ergo sum"" ("I think, therefore I am"). Methodological skepticism is distinguished from philosophical skepticism in that methodological skepticism is an approach that subjects all knowledge claims to scrutiny with the goal of sorting out true from false claims, whereas philosophical skepticism is an approach that questions the possibility of certain knowledge. Cartesian doubt is methodological. Its purpose is to use doubt as a route to certain knowledge by finding those things which could not be doubted. The fallibility of sense data in particular is a subject of Cartesian doubt. There are several interpretations
Cogito (software) on a Cogito managed repository. Conversely, most Cogito commands can be used on repositories primarily managed by Git or StGIT. Cogito is implemented as a set of Bash scripts (unlike Git, which is written mostly in C and portable Unix shell). As of April 2007 the project is stalled and declared "for sale", because a lot of the functionality has already been taken over by git, and the maintainer, Petr Baudiš, decided it would be better to focus on improving git-core. Cogito is released under the GNU GPL. As of May 2008, Cogito does not work well with recent Git