This is only an analogy, for Descartes does not posit the necessary exist, just as there always remains in a painting, however inventive and but, imaginative it may be, an irreducibly simple and real element color similarly, there is in dreams an element of noncounterfeit simpliat very dubious and uncertain; but that Arithmetic, Geometry and other sciences ofthat kind which only treat of things that are very simple and very general, without taking great trouble to ascertain whether they are actually existent or not, contain some measure of certainty and an element ofthe indubitable.