What's the difference between i.e. and e.g.?
early 13c., "to dread, fear," from Old French doter "doubt, be doubtful; be afraid," from Latin dubitare "to doubt, question, hesitate, waver in opinion" (related to dubius "uncertain;" see dubious), originally "to have to choose between two things."
The sense of "fear" developed in Old French and was passed on to English. Meaning "to be uncertain" is attested in English from c.1300. The -b- was restored 14c. by scribes in imitation of Latin. Replaced Old English tweogan (noun twynung), from tweon "two," on notion of "of two minds" or the choice of two implied in Latin dubitare (cf. German Zweifel "doubt," from zwei "two").
early 13c., from Old French dote (11c.) "fear, dread; doubt," from doter (see doubt (v.)).
in Cartesian philosophy, a way of searching for certainty by systematically though tentatively doubting everything. First, all statements are classified according to type and source of knowledge-e.g., knowledge from tradition, empirical knowledge, and mathematical knowledge. Then, examples from each class are examined. If a way can be found to doubt the truth of any statement, then all other statements of that type are also set aside as dubitable. The doubt is methodic because it assures systematic completeness, but also because no claim is made that all-or even that any-statements in a dubitable class are really false or that one must or can distrust them in an ordinary sense. The method is to set aside as conceivably false all statements and types of knowledge that are not indubitably true. The hope is that, by eliminating all statements and types of knowledge the truth of which can be doubted in any way, one will find some indubitable certainties.