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, ergo sum Translation needs a larger context to determine aspect. Following John Lyons (1982), Vladimir Žegarac notes, "The temptation to use the simple present is said to arise from the lack of progressive forms in Latin and French, and from a misinterpretation of the meaning of "cogito" as habitual or generic." (Cf. gnomic aspect.) Ann Banfield writes (also following Lyons), "In order for the statement on which Descartes's argument depends to represent certain knowledge, … its tense must be a true present—in English, a progressive, … not as 'I think' but as 'I am thinking, in conformity with the general translation of