Iamindoubtastotheproprietyofmakingmyfirstmeditationsintheplaceabovementionedmatterofdiscourse; forthesearesometaphysical, andsouncommon, asnot, perhaps, , thatitmaybedeterminedwhetherthefoundationsthatIhavelaidaresufficientlysecure, , inrelationtopractice, itissometimesnecessarytoadopt, asifabovedoubt, opinionswhichwediscerntobehighlyuncertain, ashasbeenalreadysaid; butasIthendesiredtogivemyattentionsolelytothesearchaftertruth, Ithoughtthataprocedureexactlytheoppositewascalledfor, andthatIoughttorejectasabsolutelyfalseallopinionsinregardtowhichIcouldsupposetheleastgroundfordoubt, , seeingthatoursensessometimesdeceiveus, Iwaswillingtosupposethatthereexistednothingreallysuchastheypresentedtous; andbecausesomemenerrinreasoning, andfallintoparalogisms, evenonthesimplestmattersofgeometry, I, convincedthatIwasasopentoerrorasanyother, rejectedasfalseallthereasoningsIhadhithertotakenfordemonstrations; andfinally, whenIconsideredthattheverysamethoughts (presentations) whichweexperiencewhenawakemayalsobeexperiencedwhenweareasleep, whilethereisatthattimenotoneofthemtrue, Isupposedthatalltheobjects (presentations) thathadeverenteredintomymindwhenawake, , whilstIthuswishedtothinkthatallwasfalse, itwasabsolutelynecessarythatI, whothusthought, shouldbesomewhat; andasIobservedthatthistruth, Ithink, thereforeIam (COGITOERGOSUM), wassocertainandofsuchevidencethatnogroundofdoubt, howeverextravagant, couldbeallegedbythescepticscapableofshakingit, IconcludedthatImight, withoutscruple, acceptitasthefirstprincipleofthephilosophyofwhichIwasinsearch.
